Network Working Group J. Reschke
Internet-Draft greenbytes
Expires: March 28, 2005 September 27, 2004
Datatypes for WebDAV properties
draft-reschke-webdav-property-datatypes-08
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with
RFC 3668.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on March 28, 2005.
Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This specification extends the Web Distributed Authoring Protocol
(WebDAV) to support datatyping. Protocol elements are defined to let
clients and servers specify the datatype, and to instruct the WebDAV
method PROPFIND to return datatype information.
Editorial Note (To be removed by RFC Editor before publication)
Please send comments to the Distributed Authoring and Versioning
Reschke Expires March 28, 2005 [Page 1]
Internet-Draft Datatypes for WebDAV properties September 2004
(WebDAV) working group at <mailto:w3c-dist-auth@w3.org>, which may be
joined by sending a message with subject "subscribe" to
<mailto:w3c-dist-auth-request@w3.org>. Discussions of the WEBDAV
working group are archived at
<http://lists.w3.org/Archives/Public/w3c-dist-auth/>.
Note that although discussion takes place on the WebDAV working
group's mailing list, this is not a working group document.
XML versions, latest edits and the issues list for this document are
available from
<http://greenbytes.de/tech/webdav/
#draft-reschke-webdav-property-datatypes>.
Reschke Expires March 28, 2005 [Page 2]
Internet-Draft Datatypes for WebDAV properties September 2004
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Changes for PROPPATCH method . . . . . . . . . . . . . . . . . 5
4.1 Example for successful PROPPATCH . . . . . . . . . . . . . 6
4.2 Example for failed PROPPATCH . . . . . . . . . . . . . . . 7
4.3 Example for successful PROPPATCH where type
information was not preserved . . . . . . . . . . . . . . 9
5. Changes for PROPFIND method . . . . . . . . . . . . . . . . . 9
5.1 Example for PROPFIND/prop . . . . . . . . . . . . . . . . 10
6. Changes for other methods . . . . . . . . . . . . . . . . . . 11
7. Compatibility Considerations . . . . . . . . . . . . . . . . . 11
8. Internationalization Considerations . . . . . . . . . . . . . 12
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1 Normative References . . . . . . . . . . . . . . . . . . . . 12
11.2 Informative References . . . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 13
A. Change Log (to be removed by RFC Editor before publication) . 13
A.1 Since 'draft-reschke-webdav-property-datatypes-00' . . . . 13
A.2 Since 'draft-reschke-webdav-property-datatypes-01' . . . . 13
A.3 Since 'draft-reschke-webdav-property-datatypes-02' . . . . 13
A.4 Since 'draft-reschke-webdav-property-datatypes-03' . . . . 13
A.5 Since 'draft-reschke-webdav-property-datatypes-04' . . . . 14
A.6 Since 'draft-reschke-webdav-property-datatypes-05' . . . . 14
A.7 Since 'draft-reschke-webdav-property-datatypes-06' . . . . 14
A.8 Since 'draft-reschke-webdav-property-datatypes-07' . . . . 14
B. Resolved issues (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . . . . . . 14
B.1 other-method-semantics . . . . . . . . . . . . . . . . . . 14
B.2 1_clarify_scope . . . . . . . . . . . . . . . . . . . . . 14
B.3 7_discovery . . . . . . . . . . . . . . . . . . . . . . . 15
B.4 a_remove_array_example . . . . . . . . . . . . . . . . . . 15
C. Open issues (to be removed by RFC Editor prior to
publication) . . . . . . . . . . . . . . . . . . . . . . . . . 15
C.1 edit . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Intellectual Property and Copyright Statements . . . . . . . . 16
Reschke Expires March 28, 2005 [Page 3]
Internet-Draft Datatypes for WebDAV properties September 2004
1. Introduction
This specification builds on the infrastructure provided by the
WebDAV Distributed Authoring Protocol, adding support for 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). Servers that support
searching can also take advantage of known data types when doing
comparisons and sorting.
The following potential datatyping related features were deliberately
considered out of scope:
o getting "schema" information for classes of resources (set of
"required" properties, their types, display information),
o definition of a set of mandatory property types,
o discovery of supported property types,
o extensions to PROPPATCH that would allow updates to parts of a
(structured) property.
2. 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
Reschke Expires March 28, 2005 [Page 4]
Internet-Draft Datatypes for WebDAV properties September 2004
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 named
"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.
3. Overview
Although WebDAV property types can be anything that can be marshaled
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 for properties of type "xs:string".
A server may implement any combination of datatypes, both from the
XML Schema recommendation and possibly from other namespaces.
Note that a particular property can be typed for a number of reasons:
o The property is a live property with server-defined semantics and
value space.
o The property may have been set using a non-WebDAV protocol that
the server understands in addition to WebDAV.
o The type may have been specified in an extended PROPPATCH method
as defined in Section 4.
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
Reschke Expires March 28, 2005 [Page 5]
Internet-Draft Datatypes for WebDAV properties September 2004
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 successful detection and parsing of the
typed value by setting the xsi:type attribute on the property element
in the response body (this implies that it should return a
MULTISTATUS status code and a <multistatus> response body).
4.1 Example for successful PROPPATCH
>>Request
PROPPATCH /bar.html HTTP/1.1
Host: example.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<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://ns.example.org/standards/z39.50">
<D:set>
<D:prop>
<Z:released xsi:type="xs:boolean">false</Z:released>
</D:prop>
</D:set>
</D:propertyupdate>
Reschke Expires March 28, 2005 [Page 6]
Internet-Draft Datatypes for WebDAV properties September 2004
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<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://ns.example.org/standards/z39.50">
<D:response>
<D:href>http://example.org/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: example.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<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://ns.example.org/standards/z39.50">
<D:set>
<D:prop>
<Z:released xsi:type="xs:boolean">t</Z:released>
</D:prop>
</D:set>
</D:propertyupdate>
Reschke Expires March 28, 2005 [Page 7]
Internet-Draft Datatypes for WebDAV properties September 2004
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:"
xmlns:Z="http://ns.example.org/standards/z39.50">
<D:response>
<D:href>http://example.org/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 xs: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.
Note that similar error conditions can occur in the standard WebDAV
protocol even though no data type was specified: for instance, when a
client tries to set a live property for which only a certain value
space is allowed.
Reschke Expires March 28, 2005 [Page 8]
Internet-Draft Datatypes for WebDAV properties September 2004
4.3 Example for successful PROPPATCH where type information was not
preserved
>>Request
PROPPATCH /bar.html HTTP/1.1
Host: example.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:propertyupdate xmlns:D="DAV:"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:Z="http://ns.example.org/standards/z39.50">
<D:set>
<D:prop>
<Z:released xsi:type="Z:custom">t</Z:released>
</D:prop>
</D:set>
</D:propertyupdate>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:Z="http://ns.example.org/standards/z39.50">
<D:response>
<D:href>http://example.org/bar.html</D:href>
<D:propstat>
<D:prop><Z:released/></D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
In this case the request succeeded, but the server did not know how
to handle the data type "Z:custom". Therefore no data type
information was returned in the response body.
5. Changes for PROPFIND method
PROPFIND is extended to return the data type information for
properties by adding "xsi:type" attributes to the property elements
Reschke Expires March 28, 2005 [Page 9]
Internet-Draft Datatypes for WebDAV properties September 2004
unless one of the following conditions is met:
o The data type MUST be different from "xs:string" (because this can
be considered the default data type).
o The property's data type MUST NOT be defined in [RFC2518] (because
these types are already well-defined).
5.1 Example for PROPFIND/prop
>>Request
PROPFIND /bar.html HTTP/1.1
Host: example.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:propfind xmlns:D="DAV:"
xmlns:Z="http://ns.example.org/standards/z39.50">
<D:prop>
<D:getcontenttype/>
<Z:released/>
</D:prop>
</D:propfind>
Reschke Expires March 28, 2005 [Page 10]
Internet-Draft Datatypes for WebDAV properties September 2004
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:"
xmlns:Z="http://ns.example.org/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://example.org/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].
6. Changes for other methods
Servers that support other methods using the DAV:multistatus response
format (such as the REPORT method defined in [RFC3253], section 3.6)
SHOULD apply the same extensions as defined in Section 5.
7. Compatibility Considerations
This part of 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 datatype handling 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
Reschke Expires March 28, 2005 [Page 11]
Internet-Draft Datatypes for WebDAV properties September 2004
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 datatype handling either drop the "xsi:type"
attribute, or persist it along with the property value. However,
they will never indicate successful parsing of the data type by
returning back the type in the response to PROPPATCH. Thus, clients
can supply type information without having to poll for server support
in advance.
8. Internationalization Considerations
This proposal builds on [RFC2518], and inherits its
internationalizability.
9. 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.
10. Acknowledgements
This draft has benefited from thoughtful discussion by Lisa
Dusseault, Stefan Eissing, Eric Sedlar and Kevin Wiggen.
11. References
11.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2518] Goland, Y., Whitehead, E., Faizi, A., Carter, S. and D.
Jensen, "HTTP Extensions for Distributed Authoring --
WEBDAV", RFC 2518, February 1999.
[XS1] Thompson, H., Beech, D., Maloney, M., Mendelsohn, N. and
World Wide Web Consortium, "XML Schema Part 1:
Structures", W3C REC-xmlschema-1-20010502, May 2001,
<http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/>.
[XS2] Biron, P., Malhotra, A. and World Wide Web Consortium,
"XML Schema Part 2: Datatypes", W3C
REC-xmlschema-2-20010502, May 2001,
Reschke Expires March 28, 2005 [Page 12]
Internet-Draft Datatypes for WebDAV properties September 2004
<http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/>.
11.2 Informative References
[RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C. and J.
Whitehead, "Versioning Extensions to WebDAV", RFC 3253,
March 2002.
Author's Address
Julian F. Reschke
greenbytes GmbH
Salzmannstrasse 152
Muenster, NW 48159
Germany
Phone: +49 251 2807760
Fax: +49 251 2807761
EMail: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/
Appendix A. Change Log (to be removed by RFC Editor before publication)
A.1 Since 'draft-reschke-webdav-property-datatypes-00'
Editorial fixes. Changed examples to explicitly use utf-8 encoding
for HTTP content type and XML encoding. Added example for
marshalling array-typed properties.
A.2 Since 'draft-reschke-webdav-property-datatypes-01'
Fix width of artwork for IETF compliance. "Non-normative references"
-> "Informative references".
A.3 Since 'draft-reschke-webdav-property-datatypes-02'
Added marshalling for property flags such as "hidden" and
"protected". Moved array marshalling example into back section.
Added rational and description for pf:property-displayname-set.
Added acknowledgements section.
A.4 Since 'draft-reschke-webdav-property-datatypes-03'
Replaced domain names in examples according to RFC2606: "www.foo.com"
by "example.org", "www.example.com" by "ns.example.org/standards/
z39.50/standards/z39.50" and "www.w3.com/standards/z39.50" by
"ns.example.org/standards/z39.50".
Reschke Expires March 28, 2005 [Page 13]
Internet-Draft Datatypes for WebDAV properties September 2004
A.5 Since 'draft-reschke-webdav-property-datatypes-04'
Remove superfluous IP and copyright sections. Moved "Introduction"
section to front.
A.6 Since 'draft-reschke-webdav-property-datatypes-05'
Added proposal for DAV:basicsearch operators for array-typed
properties. Update all references.
A.7 Since 'draft-reschke-webdav-property-datatypes-06'
Reformat abstract. Remove property flags, displayname support and
DASL extensions.
A.8 Since 'draft-reschke-webdav-property-datatypes-07'
Rewrite Editorial Note. Get rid of unnecessary sub section titles
after removal of property flags and displayname support (no change
tracking). Some typos fixed. Add and resolve issues
"other-method-semantics", "1_clarify_scope", "7_discovery" and
"a_remove_array_example". Removed unused reference to XML spec (no
change tracking).
Appendix B. Resolved issues (to be removed by RFC Editor before
publication)
Issues that were either rejected or resolved in this version of this
document.
B.1 other-method-semantics
Type: change
julian.reschke@greenbytes.de (2004-09-15): Define semantics for other
methods such as REPORT.
Resolution (2004-09-17): Other methods using DAV:multistatus such as
REPORT SHOULD use the same extension as defined for PROPFIND.
B.2 1_clarify_scope
Type: change
<http://lists.w3.org/Archives/Public/w3c-dist-auth/2004JulSep/
0178.html>
lisa@osafoundation.org (2004-09-14): Clarify what's in scope and what
Reschke Expires March 28, 2005 [Page 14]
Internet-Draft Datatypes for WebDAV properties September 2004
is not.
Resolution (2004-09-22): Done.
B.3 7_discovery
Type: change
<http://lists.w3.org/Archives/Public/w3c-dist-auth/2004JulSep/
0174.html>
lisa@osafoundation.org (2004-09-14): Should there be a way for
clients to detect whether the server supports this feature? I would
think that would be better. However, if there's no way, then there
should be some guidance for clients along the lines of "If the client
supports this draft, the client SHOULD send data typing information
for all non-string data types, without even knowing whether the
server supports the feature."
Resolution (2004-09-22): Clarify that sending the type information to
un-extended servers is harmless, thus no in-advance discovery is
needed.
B.4 a_remove_array_example
Type: change
<http://lists.w3.org/Archives/Public/w3c-dist-auth/2004JulSep/
0213.html>
julian.reschke@greenbytes.de (2004-09-23): Remove "array" example.
Resolution (2004-09-23): Done.
Appendix C. Open issues (to be removed by RFC Editor prior to
publication)
C.1 edit
Type: edit
julian.reschke@greenbytes.de (2004-07-08): Umbrella issue for
editorial fixes/enhancements.
Reschke Expires March 28, 2005 [Page 15]
Internet-Draft Datatypes for WebDAV properties September 2004
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM 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.
Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Reschke Expires March 28, 2005 [Page 16]