Re: draft-ietf-url-process-00
Cynthia Clark (cclark@ietf.org)
Mon, 06 Jan 1997 11:31:22 -0500
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: internet-drafts@ietf.org
Cc: uri@bunyip.com
Subject: draft-ietf-url-process-00
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Sat, 4 Jan 1997 11:41:47 PST
[apologies if this is a repeat, I couldn't tell from the bounce
message whether the original went through.]
This is intended as the initial submission for the newly forming URL
working group; if you need to, call it
draft-masinter-url-process-00
================================================================
INTERNET-DRAFT Larry Masinter
<draft-ietf-url-process-00> Dan Zigmond
January 4, 1997 Harald T. Alvestrand
expires June 4, 1997
Guidelines and Process for new URL Schemes
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as ``work in
progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
Issues:
Registration process isn't really there.
Abstract
A Uniform Resource Locator (URL) is a compact string representation
of the location for a resource that is available via the Internet.
[RFC URL-SYNTAX] defines the general syntax and semantics of URLs.
This document provides guidelines for the definition of new URL
schemes and describes the process by which they are registered.
1. Introduction
In addition to specifying the general syntax for Uniform Resource
Locators, RFC 1738 defined a number of generally useful URL schemes
and promised that a mechanism for registering new schemes would be
established. Several new URLs have been proposed since that time,
but the procedure for standardizing these schemes has never been
fully defined. This document describes the current practice and
offers some guidance for authors of new schemes.
One process for defining URL schemes is via the Internet standards
process: new URL schemes should be described in standards-track
RFCs. The Internet Assigned Numbers Authority (IANA) maintains a
registry of all URL schemes defined in this way.
2. Guildelines for new URL schemes
Because new URL schemes potentially complicate client software, new
schemes must have demonstrable utility and operability, as well as
compatibility with existing URL schemes. This section elaborates
these criteria.
2.1 Syntactic compatibility
New URL schemes should follow the same syntactic conventions of
existing schemes when appropriate.
2.1.1 Use of initial "//" for Internet host addresses
Many proposed new URL schemes seem to use "://" as a kind of
indicator that what follows is a URL. However, the use of the top
level "//" is indicative of an Internet host address, and not a top
level marker.
2.1.2 Compatibility with relative URLs
URL schemes should use the generic-URL syntax if they are intended
to be used with relative URLs. A description of the allowed
relative forms should be included in the scheme's definition.
Many applications use relative URLs extensively.
o Can it be parsed according to RFC URL-SYNTAX - that is, if the tokens
"//", "/", ";", "?" and "#" are used, do they have the meaning
given in RFC URL-SYNTAX?
o Does it make sense to use it in relative URLs like those RFC
URL-SYNTAX specifies?
o If something is designed to be broken into pieces, does it
document what those pieces are, why it should be broken in this
way, and why the breaks aren't where URL-SYNTAX says that they
usually should be?
o If it has a hierarchy, does it go left-to-right and with slash
separators like RFC URL-SYNTAX? If not, why not?
2.1.3 Does it start with "ur"?
Any scheme starting with the letters "U" and "R", in particular if
it attaches any of the meanings "uniform", "universal" or
"unifying" to the first leter, is going to cause intense debate,
and generate much heat (but maybe little light).
2.2 Is the scheme well defined?
It is important that the semantics of the "resource" that a URL
"locates" be well defined. This might mean different things
depending on the nature of the URL scheme.
2.2.1 Clear mapping from other name spaces
In many cases, new URL schemes are defined as ways to translate
other protocols and name spaces into the general framework of
URLs. The "ftp" URL scheme translates from the FTP protocol, while
the "mid" URL scheme translates from the Message-ID field of
messages.
In either case, the description of the mapping must be complete,
must describe how character sets get encoded or not in URLs, must
describe exactly how all legal values of the base standard can be
represented using the URL scheme, and exactly which modifiers,
alternate forms and other artifacts from the base standards are
included or not included.
In all cases, encoding rules must be made clear: What octets are
put into the URL, and if other octets need to be represented, what
convention is used to represent them? Any departure from the %xx
convention needs special justification.
2.2.2 URL schemes associated with network protocols
Most new URL schemes are associated with network resources that
have one or several network protocols that can access them. The
'ftp', 'news', and 'http' schemes are of this nature. For such
schemes, the specification should completely describe how URLs are
translated into protocol actions in sufficient detail to make the
access of the network resource unambiguous. If an implementation
of of the URL scheme requires some configuration, the configuration
elements must be clearly identified. (For example, the 'news'
scheme, if implemented using NTTP, requires configuration of the
NTTP server.)
2.2.3 Definition of non-protocol URL schemes
In some cases, URL schemes do not have particular network protocols
associated with them, because their use is limited to contexts
where the access method is understood. This is the case, for
example, with the "cid" and "mid" URL schemes. For these URL
schemes, the specification should describe the notation of the
scheme and a complete mapping of the locator from its source.
2.2.4 Definition of URL schemes not associated with data resources
Most URL schemes locate Internet resources that correspond
to data objects that can be retrieved or modified. This is the
case with "ftp" and "http", for example. However, some URL schemes
do not; for example, the "mailto" URL scheme corresponds to an
Internet mail address.
If a new URL scheme does not locate resources that are data
objects, the properties of names in the new space must be clearly
defined.
2.2.5 Definition of operations
In some contexts (for example, HTML forms) it is possible to
specify any one of a list of operations to be performed on a
specifc URL. (Outside forms, it is generally assumed to be
something you GET.)
The URL scheme definition should describe all well-defined
operations on the URL identifier, and what they are supposed to
do.
Some URL schemes (for example, "telnet") provide location
information for hooking onto bidirectional data streams, and don't
fit the "infoaccess" paradigm of most URLs very well; this should
be documented.
NOTE: It is perfectly valid to say that "no operation apart from
GET is defined for this URL". It is also valid to say that "there's
only one operation defined for this URL, and it's not very
GET-like". The important point is that what is defined on this type
is described.
2.3 Demonstrated utility
URL schemes should have demonstrated utility. New URL schemes are
expensive things to support. Often they require special code in
browsers, proxies, and/or servers. Having a lot of ways to say the
same thing needless complicates these programs without adding value
to the Internet.
The kinds of things that are useful include:
o Things that cannot be referred to in any other way.
o Things where it is much easier to get at them using this scheme than
(for instance) a proxy gateway.
2.3.1 Proxy into HTTP/HTML
One way to provide a demonstration of utility is via a gateway
which provides objects in the new scheme for clients using an
existing protocol. It is much easier to deploy gateways to a new
service than it is to deploy browsers that understand the new URL
object.
Things to look for when thinking about a proxy are:
o Is there a single global resolution mechanism whereby any proxy can
find the referenced object?
o If not, is there a way in which the user can find any object of this
type, and "run his own proxy"?
o Are the operations mappable one-to-one (or possibly using
modifiers) to HTTP operations?
o Is the type of returned objects well defined?
* as MIME content-types?
* as something that can be translated to HTML?
o Is there running code for a proxy?
2.4 Are there security considerations?
Above and beyond the security considerations of the base mechanism
a scheme builds upon, one must think of things that can happen in
the normal course of URL usage.
In particular:
o Does the user need to be warned that such a thing is happening
without an explicit request (GET for the source of an IMG tag,
for instance)? This has implications for the design of a proxy
gateway, of course.
o Is it possible to fake URLs of this type that point to different
things in a dangerous way?
o Are there mechanisms for identifying the requester that can be
used or need to be used with this mechanism (the From: field in a
mailto: URL, or the Kerberos login required for AFS access in the
AFS: url, for instance)?
o Does the mechanism contain passwords or other security
information that are passed inside the referring document in the
clear (as in the "ftp" URL, for instance)?
2.7 Does it start with UR?
Any scheme starting with the letters "U" and "R", in particular if it
attaches any of the meanings "uniform", "universal" or "unifying" to the
first leter, is going to cause intense debate, and generate much heat (but
maybe little light).
Any such proposal should either make sure that there is a large consensus
behind it that it will be the only scheme of its type, or pick another
name.
2.5 Non-considerations
Some issues that are often raised but are not relevent to new URL
schemes include the following.
2.5.1 Is it an URL, an URN or something else?
This classification has proved interesting in theory, but not
terribly useful when evaluating schemes.
2.5.2 Are all objects acessible?
Can all objects in the world that are validly identified by a
scheme be accessed by any UA implementing it?
Sometimes the answer will be yes and sometimes no; often it will
depend on factors (like firewalls or client configuration) not
directly related to the scheme itself.
3. Revision process
NOTE: THIS SECTION IS ENTIRELY TBD. REVIEW COMMITTEE? PRIVATE URLS?
URL schemes will have either a standards track RFC, or else they
will be a registration at IANA. where include the whole draft. URL
schemes will have a review panel, appointed by IETF AD, who may not
reject a URL scheme but who may provide a 2 sentence recommendation
about the use of the URL scheme. Conflicting registrations are
possible for non-standard URL schemes, and the order in the IANA
list of conflicting registrations will be determined by a random
number generator.
4. Security considerations
New URL schemes are required to address all security considerations
in their definitions.
5. IANA considerations
This document requires IANA to register URL schemes according to
the process outlined in section 3.
6. References
[URL-SYNTAX]
Berners-Lee, Fielding, Masinter, "Uniform Resource Locators",
<draft-fielding-url-syntax-03>, will be RFC.
7..Author's Addresses
Larry Masinter
Xerox Corporation
Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304
Fax: +1-415-812-4333
EMail: masinter@parc.xerox.com
Dan Zigmond
Wink Communications
1001 Marina Village Parkway
Alameda CA 94610
Fax: +1-510-337-2960
Phone: +1-510-337-6359
Email: dan.zigmond@wink.com
Harald T. Alvestrand
UNINETT A/S
Postboks 6683 Elgeseter 7002
Trondheim, Norway
Tel: +47 73 59 70 94
EMail: Harald.T.Alvestrand@uninett.no
To: Larry Masinter <masinter@parc.xerox.com>
Cc: Cynthia Clark <cclark@ietf.org>, uri@bunyip.com, dan.zigmond@wink.com,
Subject: Re: draft-ietf-url-process-00
In-Reply-To: Your message of "Sat, 04 Jan 1997 11:41:47 PST."
<97Jan4.124147pdt."278"@palimpsest.parc.xerox.com>
Date: Mon, 06 Jan 1997 11:31:22 -0500
From: Cynthia Clark <cclark@ietf.org>
Message-Id: <9701061131.aa01256@ietf.org>
Hi Larry,
Just for your information, I am currently working on your
Internet-Draft <draft-masinter-url-process-00.txt>.
I'll probably send an announcement to the entire IETF
regarding your I-D sometime tomorrow or the next day.
Happy New Year !!
Kind Regards,
Cynthia
------------------------------------------------------
Cynthia Clark, IETF Internet-Drafts Administrator
E-mail Address preference: <cclark@ietf.org>
-------------------------------------------------------