New Internet Draft: draft-ietf-uri-urn-syntax-00

IETF URI Working Group                                         Paul E. Hoffman
Internet-Draft                                               Proper Publishing
draft-ietf-uri-urn-syntax-00                                   Ron Daniel, Jr.
Expires October 21, 1995                        Los Alamos National Laboratory


                             Generic URN Syntax

Status of this memo

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Abstract

This document defines the syntax for Uniform Resource Names (URNs). This
syntax is basically the same as the URN syntax described in RFC 1630.

This document does not cover any specific resolution schemes or the format
of resolution results. It is expected that these issues (and other
URN-related topics) will be covered in different Internet Drafts submitted
to the IETF URI Working Group.

1. Introduction

A URN (Uniform Resource Name) is the name of a resource within the context
of a larger Internet information architecture known as Uniform Resource
Identification [URIS]. The minimum set of requirements for URNs are
described in [URNR]. An overview of URN resolution is given in [URNO].

2. Syntax

URNs are simple text strings. A URN consists of two fields seperated by a
colon (:). The two fields are:
 - The type of naming authority of the URN, called the SchemeID
 - The name of the element for the URN, called the ElementID

When URNs appear in free text, or in other places where it is not known
that they are URNs, they should be shown in a separate syntactic wrapper.
The start of the wrapper is an opening angle backet (<), the string "URN"
(the case of the letters does not matter), and a delimiting colon (:). The
tail of the wrapper is a closing angle bracket (>). Freestanding URNs that
include any white space must be wrapped in this fashion.

For example, a URN stored in a database might look like:
     x-dns-2:library.bigstate.edu:aj17-mcc

The same URN, appearing in a mail message, would look like
     <urn:x-dns-2:library.bigstate.edu:aj17-mcc>

The first and SchemeID fields are case insensitive. The case sensitivity
and character set of the ElementID field depends on the value of the
SchemeID field. White space (the characters Space, Tab, CR, and LF) is
allowed but is not significant within a URN.

URNs are often displayed and transmitted in the same media as URLs. In
order to minimize problems with interoperability, encoding of characters in
URNs follow the same rules used by URLs in [URL].

2.1 SchemeIDs

The SchemeID field describes what kind of naming authority is used. This is
the authority by which the ElementIDs are defined.

SchemeIDs are case insensitive identifiers of the URN resolution scheme
used to resolve a URN. SchemeIDs starting with the characters "x-" are
reserved for experimental purposes. Because all URN schemes are currently
experimental, all URN SchemeIDs should begin with "x-" until the schemes
are approved by the IETF URI Working Group. The Internet Assigned Numbers
Authority (IANA) will maintain a registry of SchemeIDs.

2.2 ElementIDs

The ElementID is the element that will be resolved. It is important to note
that this is not the "name" part of the URN: the combination of the three
fields in a URN is the only definition of the resource's name. For example,
consider the two URNs:
<urn:x-dns-2:physics.bigstate.edu:thesis12>
<urn:x-wlnk:physics.bigstate.edu:thesis12>
They might be names of completely different Internet resources, similar
resources, or even the same resource. However, even though the ElementIDs
are the same in the two URNs, the two URNs are different.

For all Element IDs in all SchemeIDs, the characters "#" (hex 23) and "?"
(hex 3F) are reserved for future use. Also, ">" (hex 3E) is reserved since
it is the wrapper closing character. The ":" (hex 3A) character is not
reserved, but its semantics of seperating fields should not be casually
ignored.

3. Security Implications

Although there are security implications in resolving URNs, there are no
security implications in defining their syntax.

4. References

[URIS] RFC 1630, "Universal Resource Identifiers in WWW".

[URL] RFC 1738, "Uniform Resource Locators (URL)".

[URNO] Internet-Draft, "URN Resolution Overview". The name of the draft at
the time of this writing is "draft-ietf-uri-urn-res-descrip-00".

[URNR] RFC 1737, "Functional Requirements for Uniform Resource Names".

5. Author Contact Information

Paul E. Hoffman
Proper Publishing
127 Segre Place
Santa Cruz, CA, USA  95060
voice:  (408) 426-6222
phoffman@proper.com

Ron Daniel Jr.
MS B287
Los Alamos National Laboratory
Los Alamos, NM, USA 87545
voice:  (505) 665-0597
fax:  (505) 665-4939
rdaniel@lanl.gov

Received on Monday, 1 May 1995 12:19:06 UTC