- From: Julian Reschke <julian.reschke@gmx.de>
- Date: Fri, 8 Jun 2001 18:10:22 +0200
- To: "WebDAV WG" <w3c-dist-auth@w3.org>
- Message-ID: <JIEGINCHMLABHJBIGKBCCEKMCGAA.julian.reschke@gmx.de>
> From: Julian Reschke [mailto:julian.reschke@gmx.de]
> Sent: Thursday, May 10, 2001 9:02 PM
> To: WebDAV WG
> Subject: Proposal for marshalling property type information
>
>
> Hi,
>
> attached is a an attempt to define a way to marshall datatype
> information for WebDAV properties in terms of XML Schema (part
> 2). (the archive contains an HTML version and an XML version
> conforming to the RFC2629 DTD).
>
> Feedback appreciated.
I didn't get any feedback, therefore I am retrying with a plain text version
of the proposal :-)
Julian
--
Network Working Group J. Reschke
Internet-Draft greenbytes
Expires: December 7, 2001 June 8, 2001
Datatypes for WebDAV properties
draft-reschke-webdav-property-datatypes-00
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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-
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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."
The list of current Internet-Drafts can be accessed at
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This Internet-Draft will expire on December 7, 2001.
Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
This specification extends the WebDAV Distributed Authoring Protocol
to support datatyping on property values. Protocol elements are
defined to let clients and servers specify the type of a property,
and to instruct the WebDAV method PROPFIND to return datatype
information.
Distribution of this document is unlimited. Please send comments to
the Distributed Authoring and Versioning (WebDAV) working group at
w3c-dist-auth@w3.org[1], which may be joined by sending a message
with subject "subscribe" to w3c-dist-auth-request@w3.org[2].
Discussions of the WEBDAV working group are archived at URL:
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http://lists.w3.org/Archives/Public/w3c-dist-auth/.
Table of Contents
1. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview of data types . . . . . . . . . . . . . . . . . . . . 5
4. Changes for PROPPATCH method . . . . . . . . . . . . . . . . . 6
4.1 Example for successful PROPPATCH . . . . . . . . . . . . . . . 6
4.2 Example for failed PROPPATCH . . . . . . . . . . . . . . . . . 7
5. Changes for PROPFIND method . . . . . . . . . . . . . . . . . 9
5.1 Example for PROPFIND/prop . . . . . . . . . . . . . . . . . . 9
6. Compatibility Considerations . . . . . . . . . . . . . . . . . 11
7. Internationalization Considerations . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
9. Copyright . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10. Intellectual Property . . . . . . . . . . . . . . . . . . . . 15
References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 16
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 17
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1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The term "property element" refers to the XML element that identifies
a particular property, for instance
<getcontentlength xmlns="DAV:" />
The term "prop element" is used for the WebDAV "prop" element as
defined in section 12.11 of [RFC2518].
The XML representation of schema components uses a vocabulary
identified by the namespace name "http://www.w3.org/2001/XMLSchema".
For brevity, the text and examples in this specification use the
prefix "xs:" to stand for this namespace; in practice, any prefix can
be used. "XML Schema: Structures" ([XS1]) also defines several
attributes for direct use in any XML documents. These attributes are
in a different namespace, which has the namespace name
"http://www.w3.org/2001/XMLSchema-instance". For brevity, the text
and examples in this specification use the prefix "xsi:" to stand for
this latter namespace; in practice, any prefix can be used.
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2. Introduction
This specification builds on the infrastructure provided by the
WebDAV Distributed Authoring Protocol, adding support data-typed
properties.
Although servers must support XML content in property values, it may
be desirable to persist values as scalar values when possible, and to
expose the data's type when the property value is returned to the
client. The client is free to ignore this information, but it may be
able to take advantage of it when modifying a property.
On the other hand, when setting new properties, it can be desirable
to pass data type information along with the value. A server can
take advantage of this information to optimize storage and to perform
additional parsing (for instance of dates).
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3. Overview of data types
Although WebDAV property types can be anything that can be marshalled
as content of an XML element, in many cases they actually are simple
types like integers, booleans or dates. "XML Schema Part 2:
Datatypes" [XS2] defines a set of simple types which can be used as a
basis for supplying type information to attributes.
Data type information is represented using the attribute "type" from
the XML Schema namespace "http://www.w3.org/2001/XMLSchema-instance".
In XML Schema, data types are qualified names, and the XML Schema
recommendation defines a set of built-in datatypes (section 3 of
[XS2]), defined in the namespace "http://www.w3.org/2001/XMLSchema".
To avoid unnecessary verbosity, data type information should only be
supplied if it adds usable information to the protocol. In
particular, type information is not required for live properties
defined in WebDAV [RFC2518] and related standards and properties of
type "xs:string".
A server may implement any combination of datatypes, both from the
XML Schema recommendation and possibly from other namespaces.
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4. Changes for PROPPATCH method
If the property element has an XML attribute named "xsi:type", the
server may use this information to select an optimized representation
for storing the property value. For instance, by specifying a type
as "xs:boolean", the client declares the property value to be of type
boolean (as defined in [XS2]). The server may choose any suitable
internal format for persisting this property, and in particular is
allowed to fail the request if the format given does not fit the
format defined for this type.
The server should indicate successfull detection and parsing of the
typed value by setting the xsi:type attribute on the property element
in the response body.
4.1 Example for successful PROPPATCH
>>Request
PROPPATCH /bar.html HTTP/1.1
Host: www.foo.com
Content-Type: text/xml
Content-Length: xxxx
<D:propertyupdate xmlns:D="DAV:"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:Z="http://www.w3.com/standards/z39.50">
<D:set>
<D:prop>
<Z:released xsi:type="xs:boolean">false</Z:released>
</D:prop>
</D:set>
</D:propertyupdate>
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>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxx
<D:multistatus xmlns:D="DAV:"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:Z="http://www.w3.com/standards/z39.50">
<D:response>
<D:href>http://www.foo.com/bar.html</D:href>
<D:propstat>
<D:prop><Z:released xsi:type="xs:boolean" /></D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
In this cases, the xsi:type attribute on the element "Z:released"
indicates that the server indeed has understood the submitted data
type information.
4.2 Example for failed PROPPATCH
>>Request
PROPPATCH /bar.html HTTP/1.1
Host: www.foo.com
Content-Type: text/xml
Content-Length: xxxx
<D:propertyupdate xmlns:D="DAV:"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:Z="http://www.w3.com/standards/z39.50">
<D:set>
<D:prop>
<Z:released xsi:type="xs:boolean">t</Z:released>
</D:prop>
</D:set>
</D:propertyupdate>
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>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxx
<D:multistatus xmlns:D="DAV:"
xmlns:Z="http://www.w3.com/standards/z39.50">
<D:response>
<D:href>http://www.foo.com/bar.html</D:href>
<D:propstat>
<D:prop><Z:released/></D:prop>
<D:status>HTTP/1.1 422 Unprocessable Entity</D:status>
<D:responsedescription>Does not parse as
xsd:boolean</D:responsedescription>
</D:propstat>
</D:response>
</D:multistatus>
In this case the request failed because the supplied value "t" is not
a valid representation for a boolean value.
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5. Changes for PROPFIND method
PROPFIND is extended to return the data type information for
properties that satisfy the following conditions:
o The data type is different from "xs:string".
o The property's data type is not defined in [RFC2518] or a related
specification.
5.1 Example for PROPFIND/prop
>>Request
PROPFIND /bar.html HTTP/1.1
Host: www.foo.com
Content-Type: text/xml
Content-Length: xxxx
<D:propfind xmlns:D="DAV:"
xmlns:Z="http://www.w3.com/standards/z39.50">
<D:prop>
<D:getcontenttype/>
<Z:released/>
</D:prop>
</D:propfind>
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>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxx
<D:multistatus xmlns:D="DAV:"
xmlns:Z="http://www.w3.com/standards/z39.50"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xs="http://www.w3.org/2001/XMLSchema">
<D:response>
<D:href>http://www.foo.com/bar.html</D:href>
<D:propstat>
<D:prop>
<D:getcontenttype>text/html</D:getcontenttype>
<Z:released xsi:type="xs:boolean">1</Z:released>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
This example shows that the property value "true" is returned with
the correct data type information, and that the server chose one of
the two possible representations defined in XML Schema. It also
shows that data type information is not returned for
"D:getcontenttype", as this property's data type is already defined
in [RFC2518].
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6. Compatibility Considerations
This specification does not introduce any new protocol elements, nor
does it change the informal WebDAV DTD. It merely specifies
additional server semantics for the case where clients submit
additional data type information in an attribute on the property
element (previously undefined), and adds an additional attribute on
property elements upon PROPFIND.
Clients not aware of this specification should not supply the
"xsi:type" attribute on property elements (after all, this attribute
belongs to the XML Schema-Instance namespace which has been defined
for exactly this purpose). Old clients should also ignore additional
attributes on property elements returned by PROPFIND (and similar
methods), although the WebDAV specification only defines this
behaviour for unknown elements (and is silent about unknown
attributes).
Servers not aware of this specification either drop the "xsi:type"
attribute, or persist it along with the property value. However,
they will never indicate successfull parsing of the data type by
returning back the type in the response to PROPPATCH.
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7. Internationalization Considerations
This proposal builds on [RFC2518], and inherits its
internationalizability.
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8. IANA Considerations
This proposal does not introduce any new IANA considerations, since
it does not specify any new namespaces (in the general sense), but
merely uses existing ones.
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9. Copyright
To be supplied by the RFC Editor.
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10. Intellectual Property
To be supplied by the RFC Editor.
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References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[XML] Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E. and
World Wide Web Consortium, "Extensible Markup Language
(XML) 1.0", W3C XML, February 1998,
<http://www.w3.org/TR/1998/REC-xml-19980210>.
[XS1] Thompson, H., Beech, D., Maloney, M., Mendelsohn, N. and
World Wide Web Consortium, "XML Schema Part 1:
Structures", W3C XS1, May 2001,
<http://www.w3.org/TR/xmlschema-1/>.
[XS2] Biron, P., Malhotra, A. and World Wide Web Consortium,
"XML Schema Part 2: Datatypes", W3C XS2, May 2001,
<http://www.w3.org/TR/xmlschema-2/>.
[RFC2518] Goland, Y., Whitehead, E., Faizi, A., Carter, S. and D.
Jensen, "HTTP Extensions for Distributed Authoring --
WEBDAV", RFC 2518, February 1999.
[1] <mailto:w3c-dist-auth@w3.org>
[2] <mailto:w3c-dist-auth-request@w3.org?subject=subscribe>
Author's Address
Julian F. Reschke
greenbytes GmbH
Salzmannstrasse 152
Muenster, NW 48159
Germany
EMail: julian.reschke@greenbytes.de
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Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
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The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Reschke Expires December 7, 2001 [Page 17]
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Received on Friday, 8 June 2001 12:10:36 UTC