Network Working Group                                         J. Reschke
Request for Comments: 4316                                    greenbytes
Category: Experimental                                     December 2005


   Datatypes for Web Distributed Authoring and Versioning (WebDAV)
                              Properties

Status of This Memo

  This memo defines an Experimental Protocol for the Internet
  community.  It does not specify an Internet standard of any kind.
  Discussion and suggestions for improvement are requested.
  Distribution of this memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (2005).

Abstract

  This specification extends the Web Distributed Authoring and
  Versioning 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.

Table of Contents

  1. Introduction ....................................................2
  2. Notational Conventions ..........................................2
  3. Overview ........................................................3
  4. Changes for PROPPATCH Method ....................................4
     4.1. Example of Successful PROPPATCH ............................4
     4.2. Example of Failed PROPPATCH ................................5
     4.3. Example of Successful PROPPATCH Where Type
          Information Was Not Preserved ..............................6
  5. Changes for PROPFIND Method .....................................7
     5.1. Example of PROPFIND/prop ...................................7
  6. Changes for Other Methods .......................................8
  7. Compatibility Considerations ....................................8
  8. Internationalization Considerations .............................9
  9. Security Considerations .........................................9
  10. Acknowledgements ...............................................9
  11. References .....................................................9
     11.1. Normative References ......................................9
     11.2. Informative References ....................................9




Reschke                       Experimental                      [Page 1]

RFC 4316            Datatypes for WebDAV Properties        December 2005


1.  Introduction

  This specification builds on the infrastructure provided by the Web
  Distributed Authoring and Versioning (WebDAV) 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 datatype 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 datatypes 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
  identified by the namespace name "http://www.w3.org/2001/XMLSchema".



Reschke                       Experimental                      [Page 2]

RFC 4316            Datatypes for WebDAV Properties        December 2005


  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 Part 1: 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 that can be used as a
  basis for supplying type information to attributes.

  Datatype information is represented using the attribute "type" from
  the XML Schema namespace "http://www.w3.org/2001/XMLSchema-instance".
  In XML Schema, datatypes 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, datatype 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.










Reschke                       Experimental                      [Page 3]

RFC 4316            Datatypes for WebDAV Properties        December 2005


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 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 of 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>

  >>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">



Reschke                       Experimental                      [Page 4]

RFC 4316            Datatypes for WebDAV Properties        December 2005


    <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 case, the xsi:type attribute on the element "Z:released"
  indicates that the server indeed has understood the submitted data
  type information.

4.2.  Example of 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>

  >>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>



Reschke                       Experimental                      [Page 5]

RFC 4316            Datatypes for WebDAV Properties        December 2005


        <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 datatype was specified: for instance, when a
  client tries to set a live property for which only a certain value
  space is allowed.

4.3.  Example of 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>



Reschke                       Experimental                      [Page 6]

RFC 4316            Datatypes for WebDAV Properties        December 2005


      <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 datatype "Z:custom".  Therefore, no datatype
  information was returned in the response body.

5.  Changes for PROPFIND Method

  PROPFIND is extended to return the datatype information for
  properties by adding "xsi:type" attributes to the property elements
  unless one of the following conditions is met:

  o  The datatype MUST be different from "xs:string" (because this can
     be considered the default datatype).

  o  The property's datatype MUST NOT be defined in [RFC2518] (because
     these types are already well-defined).

5.1.  Example of 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>

  >>Response

  HTTP/1.1 207 Multi-Status
  Content-Type: text/xml; charset="utf-8"
  Content-Length: xxxx

  <?xml version="1.0" encoding="utf-8" ?>



Reschke                       Experimental                      [Page 7]

RFC 4316            Datatypes for WebDAV Properties        December 2005


  <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 datatype information and that the server chose one of the
  two possible representations defined in XML Schema.  It also shows
  that datatype information is not returned for "D:getcontenttype", as
  this property's datatype 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 datatype 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
  for exactly this purpose; see [XS1], Section 2.6.1).  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 (see [RFC2518], Section 23.3.2.2).

  Servers not aware of datatype handling either drop the "xsi:type"
  attribute or have it persist along with the property value (see



Reschke                       Experimental                      [Page 8]

RFC 4316            Datatypes for WebDAV Properties        December 2005


  [RFC2518], Section 4.4).  However, they will never indicate
  successful parsing of the datatype 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.  Security Considerations

  This protocol extension does not introduce any new security
  implications beyond those documented for the base protocol (see
  [RFC2518], Section 17).

10.  Acknowledgements

  This document 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
             Second Edition", W3C REC-xmlschema-1-20041028,
             October 2004,
             <http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/>.

  [XS2]      Biron, P., Malhotra, A., and World Wide Web Consortium,
             "XML Schema Part 2: Datatypes Second Edition", W3C REC-
             xmlschema-2-20041028, October 2004,
             <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/>.

11.2.  Informative References

  [RFC3253]  Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J.
             Whitehead, "Versioning Extensions to WebDAV", RFC 3253,
             March 2002.



Reschke                       Experimental                      [Page 9]

RFC 4316            Datatypes for WebDAV Properties        December 2005


Author's Address

  Julian F. Reschke
  greenbytes GmbH
  Hafenweg 16
  Muenster, NW  48155
  Germany

  Phone: +49 251 2807760
  Fax:   +49 251 2807761
  EMail: [email protected]
  URI:   http://greenbytes.de/tech/webdav/







































Reschke                       Experimental                     [Page 10]

RFC 4316            Datatypes for WebDAV Properties        December 2005


Full Copyright Statement

  Copyright (C) The Internet Society (2005).

  This document is subject to the rights, licenses and restrictions
  contained in BCP 78 and at www.rfc-editor.org/copyright.html, and
  except as set forth therein, the authors retain all their rights.

  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.

Intellectual Property

  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-
  [email protected].

Acknowledgement

  Funding for the RFC Editor function is currently provided by the
  Internet Society.







Reschke                       Experimental                     [Page 11]


You are viewing proxied material from gopher.rbfh.de. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.