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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 4316

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.

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   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



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   (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>.






































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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











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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



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   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



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   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>



















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   >>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>







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   >>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.























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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



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   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>

























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   >>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



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   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,



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              <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".



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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



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   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.








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Internet-Draft      Datatypes for WebDAV properties       September 2004


Intellectual Property Statement

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Reschke                  Expires March 28, 2005                [Page 16]


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