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Versions: (draft-ietf-simple-xcap-package) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 RFC 5874

SIMPLE                                                      J. Rosenberg
Internet-Draft                                                     Cisco
Intended status: Standards Track                           J. Urpalainen
Expires: February 18, 2008                                         Nokia
                                                         August 17, 2007


  An Extensible Markup Language (XML) Document Format for Indicating A
     Change in XML Configuration Access  Protocol (XCAP) Resources
                     draft-ietf-simple-xcap-diff-06

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on February 18, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This specification defines a document format that can be used to
   indicate that a change has occurred in a document managed by the
   Extensible Markup Language (XML) Configuration Access Protocol
   (XCAP).  This format indicates the document that has changed and its
   former and new entity tags.  It also can indicate the specific change
   that was made in the document, using an XML patch format.  This



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   format allows also indications of element and attribute content of an
   XML document.  XCAP diff documents can be delivered to clients using
   a number of means, including a Session Initiation Protocol (SIP)
   event package.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Structure of an XCAP Diff Document . . . . . . . . . . . . . .  4
   4.  XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  Example Document . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
     7.1.  application/xcap-diff+xml MIME Type  . . . . . . . . . . . 11
     7.2.  URN Sub-Namespace Registration for
           urn:ietf:params:xml:ns:xcap-diff . . . . . . . . . . . . . 12
     7.3.  Schema Registration  . . . . . . . . . . . . . . . . . . . 12
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 13
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 13
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
   Intellectual Property and Copyright Statements . . . . . . . . . . 15


























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1.  Introduction

   The Extensible Markup Language (XML) Configuration Access Protocol
   (XCAP) [9] is a protocol that allows clients to manipulate XML
   documents stored on a server.  These XML documents serve as
   configuration information for application protocols.  As an example,
   resource list [13] subscriptions (also known as presence lists) allow
   a client to have a single SIP subscription to a list of users, where
   the list is maintained on a server.  The server will obtain presence
   for those users and report it back to the client.  This application
   requires the server, called a Resource List Server (RLS), to have
   access to the list of presentities.  This list needs to be
   manipulated by clients so they can add and remove their friends as
   they desire.

   Complexities arise when multiple clients attempt to simultaneously
   manipulate a document, such as a presence list.  Frequently, a client
   will keep a copy of the current list in memory, so it can render it
   to users.  However, if another client modifies the document, the
   cached version becomes stale.  This modification event must be made
   known to all clients which have cached copies of the document, so
   that they can fetch the most recent one.

   To deal with this problem, clients can use a Session Initiation
   Protocol (SIP) [11] event package [12] to subscribe to change events
   in XCAP documents.  This notification needs to indicate the specific
   resource that changed, and how it changed.  One solution for the
   format of such a change notification would be a content indirection
   object [15].  Though content indirection can tell a client that a
   document has changed, it provides it with MIME Content-ID indicating
   the new version of the document.  The MIME Content-ID is not the same
   as the entity tag, which is used by XCAP for document versioning.  As
   such, a client cannot easily ascertain whether an indication of a
   change in a document is due to a change it just made, or due to a
   change another client made at around the same time.  Furthermore,
   content indirections don't indicate how a document changed; they
   would only be able to indicate that it did change.

   To resolve these problems, this document defines a data format which
   can convey the fact that an XML document managed by XCAP has changed.
   This data format is an XML document format, called an XCAP diff
   document.  This format can indicate that a document has changed, and
   provide its previous and new entity tags.  It can also optionally
   include a set of patch operations [10], which indicate how to
   transform the document from the version prior to the change, to the
   version after it.  XML element and attribute content of XCAP
   documents can also be delivered with this format.




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   XML documents that are equivalent for the purposes of many
   applications may differ in their physical representation.  Similar to
   XCAP, the canonical form with comments [1] of an XML document
   determines the logical equivalence when this format is used to patch
   XML documents.


2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in RFC 2119 [8] and
   indicate requirement levels for compliant implementations.

   This specification also defines the following additional terms:

   Document:  When the term document is used without the "XCAP diff" in
      front of it, it refers to the XCAP document resource about whom
      the XCAP diff document is reporting a change.

   XCAP diff document:  The XML document defined by this specification
      that reports on a set of changes in an XCAP document resource.

   Server:  Typically an XCAP server, this is a protocol entity that
      generates XCAP diff documents based on its knowledge of a set of
      XCAP documents.

   Client:  Typically an XCAP client and SIP User Agent (UA), the client
      consumes XCAP diff documents in order to reconstruct the document
      stored on the server.


3.  Structure of an XCAP Diff Document

   An XCAP diff document is an XML [2] document that MUST be well-formed
   and SHOULD be valid.  XCAP diff documents MUST be based on XML 1.0
   and MUST be encoded using UTF-8.  This specification makes use of XML
   namespaces for identifying XCAP diff documents and document
   fragments.  The namespace URI for elements defined by this
   specification is a URN [4], using the namespace identifier 'ietf'
   defined by [6] and extended by [7].  This URN is:

      urn:ietf:params:xml:ns:xcap-diff

   An XCAP diff document begins with the root element tag <xcap-diff>.
   This element has a single mandatory attribute, "xcap-root".  The
   value of this attribute is the XCAP root URI for the documents in
   which the changes have taken place.  A single XCAP diff document can



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   only represent changes in documents within the same XCAP root.  The
   content of the <xcap-diff> element is an unordered sequence of
   <document>, <element> and <attribute> elements followed by any number
   of elements from other namespaces for the purposes of extensibility.
   Any such unknown elements MUST be ignored by the client.  Each
   <document> element specifies changes in a specific document within
   the XCAP root.  It has one mandatory attribute, "sel", and a two
   optional attributes, "new-etag" and "previous-etag".  The "sel"
   attribute of the <document> element identifies the specific document
   within the XCAP root for which changes are indicated.  Its content
   MUST be a relative path reference, with the base URI being equal to
   the XCAP root URI.  The "new-etag" attribute provides the entity tag
   (ETag) for the document after the application of the changes,
   assuming the document exists after those changes.  The "previous-
   etag" attribute provides an identifier for the document instance
   prior to the change.  If the change being reported is the removal of
   a document, the "previous-etag" MUST only be included and the "new-
   etag" attribute will not be present.  The "new-etag" attribute MUST
   only exist alone when the document either exists or it was just
   created (no patch included).  Both attributes are present when a
   patch (or series of XCAP operations) has been applied to the
   resource.  Also both attributes MAY be used to indicate an ETag
   change without any document modifications (patches).

   The "previous-etag" and "new-etag" need not have been sequentially
   assigned ETags at the server.  An XCAP diff document can indicate
   changes that have occurred over a series of XCAP operations.  The
   only requirement then is that, the sequence of events, when executed
   serially, will result in the transformation of the document with the
   ETag "previous-etag" to the one whose ETag is "new-etag".  Also the
   series of operations do not have to be the same exact series of
   operations that occurred at the server.

   Each <document> element contains either a sequence of patching
   instructions or an indication that the body hasn't semantically
   changed.  The latter means that the document has been assigned a new
   ETag but its content is unchanged and it is indicated by the <body-
   not-changed> element.  Patching instructions are described by the
   <add>, <replace> and <remove> elements.  These elements use the
   corresponding add, replace and remove types defined in [10], and
   define a set of patch operations that can be applied to transform the
   document.  See [10] for instructions on how this transformation is
   effected.  The <document> element can also contain elements from
   other namespaces for the purposes of extensibility.  Any unknown
   elements MUST be ignored.






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   Figure 1 shows <document> element content and how corresponding
   resource or metadata changes.  An external document retrieval means
   in practice an HTTP GET requests for a relevant resource.


   +-----------+----------+-----------+----------+-------------------+
   | previous- | new-     | <add>     | <body-   | XCAP resource/    |
   | etag      | etag     | <replace> | not-     | metadata change   |
   |           |          | <remove>  | changed> |                   |
   +-----------+----------+-----------+----------+-------------------+
   | xxx       | yyy      | *         | -        | resource patched, |
   |           |          |           |          | patch included    |
   +-----------+----------+-----------+----------+-------------------+
   | xxx       | yyy      | -         | -        | resource patched, |
   |           |          |           |          | external document |
   |           |          |           |          | retrieval         |
   +-----------+----------+-----------+----------+-------------------+
   | xxx       | yyy      | -         | *        | only ETag changed |
   +-----------+----------+-----------+----------+-------------------+
   | -         | yyy      | -         | -        | resource created  |
   |           |          |           |          | or exists,        |
   |           |          |           |          | external document |
   |           |          |           |          | retrieval         |
   +-----------+----------+-----------+----------+-------------------+
   | xxx       | -        | -         | -        | resource removed  |
   +-----------+----------+-----------+----------+-------------------+


   Figure 1: <document> element content / corresponding resource changes

   Each <element> element indicates the existing element content of an
   XCAP document.  It has one mandatory attribute, "sel", and one
   optional attribute, "exists".  The "sel" attribute of the <element>
   element identifies an XML element of an XCAP document.  It is a
   percent endoced relative URI following XCAP conventions when
   selecting elements.  The XCAP Node Selector MUST always locate a
   unique node, the "exists" attribute thus shows whether an element
   exists or not in the XCAP document.  When the "exists" attribute is
   absent from the <element> element, the indicated element still exists
   in the XCAP document.  The located result element exists as a child
   element of the <element> element.  It should be noted, that only the
   full content of an element is shown if it exists, there are no
   conventions for patching these elements.  In a corner case where the
   content of this element cannot be presented for some reason, although
   it exists in the XCAP document, the <element> element MUST not have
   any child nodes.

   As the result XML element is typically namespace qualified, all



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   needed namespace declarations MUST exist within the <xml-diff>
   document.  The possible local namespace declarations within the
   result element exist unmodified as in the source document, similar to
   XCAP conventions.  Other namespace references MUST be resolved from
   the context of the <element> or its parent elements.  The prefixes of
   qualified names (QName) [3] of XML nodes also remain as they exist
   originally in the source XCAP document.

   Each <attribute> element indicates the existing attribute content of
   an XCAP document.  It has one mandatory attribute, "sel", and one
   optional attribute, "exists".  The "sel" attribute of the <attribute>
   element identifies an XML attribute of an XCAP document.  It is a
   percent endoced relative URI following XCAP conventions when
   selecting attributes.  The "exists" attribute indicates whether an
   attribute exists or not in the XCAP document.  When the "exists"
   attribute is absent from the <attribute> element, the indicated
   attribute exists in the XCAP document.  The child text node of the
   <attribute> element indicates the value of the located attribute.


4.  XML Schema

   The XML Schema for the XCAP diff format.

  <?xml version="1.0" encoding="UTF-8"?>
  <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
   xmlns="urn:ietf:params:xml:ns:xcap-diff"
   targetNamespace="urn:ietf:params:xml:ns:xcap-diff"
   elementFormDefault="qualified"
   attributeFormDefault="unqualified">

   <!-- include patch-ops -->
   <xs:include
    schemaLocation="urn:ietf:params:xml:schema:xml-patch-ops"/>

   <!-- document root -->
   <xs:element name="xcap-diff">
    <xs:complexType>
     <xs:sequence minOccurs="0">

      <xs:sequence minOccurs="0" maxOccurs="unbounded">
       <xs:choice>
        <xs:element name="document" type="documentType"/>
        <xs:element name="element" type="elementType"/>
        <xs:element name="attribute" type="attributeType"/>
       </xs:choice>
      </xs:sequence>




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      <xs:any namespace="##other" processContents="lax"
              minOccurs="0" maxOccurs="unbounded"/>

     </xs:sequence>
     <xs:attribute name="xcap-root" type="xs:anyURI" use="required"/>
     <xs:anyAttribute namespace="##any" processContents="lax"/>
    </xs:complexType>
   </xs:element>

   <!-- xcap document type -->
   <xs:complexType name="documentType">

    <xs:choice minOccurs="0">
     <xs:element name="body-not-changed" type="emptyType"/>

     <xs:sequence minOccurs="0" maxOccurs="unbounded">
      <xs:choice>

       <xs:element name="add">
        <xs:complexType>
         <xs:complexContent>
          <xs:extension base="add">
           <xs:anyAttribute processContents="lax"/>
          </xs:extension>
         </xs:complexContent>
        </xs:complexType>
       </xs:element>

       <xs:element name="remove">
        <xs:complexType>
         <xs:complexContent>
          <xs:extension base="remove">
           <xs:anyAttribute processContents="lax"/>
          </xs:extension>
         </xs:complexContent>
        </xs:complexType>
       </xs:element>

       <xs:element name="replace">
        <xs:complexType>
         <xs:complexContent>
          <xs:extension base="replace">
           <xs:anyAttribute processContents="lax"/>
          </xs:extension>
         </xs:complexContent>
        </xs:complexType>
       </xs:element>




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       <xs:any namespace="##other" processContents="lax"/>
      </xs:choice>
     </xs:sequence>

    </xs:choice>

    <xs:attribute name="sel" type="xs:anyURI" use="required"/>
    <xs:attribute name="new-etag" type="xs:string" use="optional"/>
    <xs:attribute name="previous-etag" type="xs:string" use="optional"/>
    <xs:anyAttribute namespace="##any" processContents="lax"/>
   </xs:complexType>

   <!-- xcap element type -->
   <xs:complexType name="elementType">
    <xs:complexContent>
     <xs:restriction base="xs:anyType">
      <xs:sequence>
       <xs:any processContents="lax" namespace="##any"
               minOccurs="0" maxOccurs="1"/>
      </xs:sequence>
      <xs:attribute name="sel" type="xs:string"
                    use="required"/>
      <xs:attribute name="exists" type="xs:boolean"/>
     </xs:restriction>
    </xs:complexContent>
   </xs:complexType>

   <!-- xcap attribute type -->
   <xs:complexType name="attributeType">
    <xs:simpleContent>
     <xs:extension base="xs:string">
      <xs:attribute name="sel" type="xs:string"
                    use="required"/>

      <xs:attribute name="exists" type="xs:boolean"/>
     </xs:extension>
    </xs:simpleContent>
   </xs:complexType>

   <!-- empty type -->
   <xs:complexType name="emptyType"/>

  </xs:schema>








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5.  Example Document

   The following is an example of a document compliant to the schema.

  <?xml version="1.0" encoding="UTF-8"?>
  <xcap-diff xmlns="urn:ietf:params:xml:ns:xcap-diff"
             xcap-root="http://xcap.example.com/root/">

   <document new-etag="7ahggs"
             sel="resource-lists/users/sip:joe@example.com/coworkers"
             previous-etag="8a77f8d"/>

   <d:element sel="rls-services/users/sip:joe@example.com/index/~~
  /*/service%5b@uri='sip:marketing@example.com'%5d"
            xmlns:d="urn:ietf:params:xml:ns:xcap-diff"
            xmlns="urn:ietf:params:xml:ns:rls-services"
            xmlns:rl="urn:ietf:params:xml:ns:resource-lists"
      ><service uri="sip:marketing@example.com">
        <list name="marketing">
          <rl:entry uri="sip:joe@example.com"/>
          <rl:entry uri="sip:sudhir@example.com"/>
        </list>
        <packages>
          <package>presence</package>
        </packages>
      </service></d:element>

   <attribute
    sel="rls-services/users/sip:joe@example.com/index/~~/*/service/@uri"
        >sip:marketing@example.com</attribute>

  </xcap-diff>


   This indicates that the document with URI "http://xcap.example.com/
   root/resource-lists/users/sip:joe@example.com/coworkers" has changed.
   Its previous entity tag is "8a77f8d" and its new one is "7ahggs" but
   actual changes are not shown.  The <service> element exists in the
   rls-services "index" document and its full content is shown.  Note
   that the <service> element is attached with a default namespace
   declaration within the original document.  Similarly, a "uri"
   attribute content is shown from the same "index" document as an
   illustrative example.


6.  Security Considerations

   XCAP diff documents can include changes from one document to another.



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   As a consequence, if the document itself is sensitive and requires
   confidentiality, integrity or authentication, then the same applies
   to the XCAP diff format.  Therefore, protocols which transport XCAP
   diff documents must provide sufficient security capabilities for
   transporting the document itself.


7.  IANA Considerations

   There are several IANA considerations associated with this
   specification.

7.1.  application/xcap-diff+xml MIME Type

      MIME media type name: application

      MIME subtype name: xcap-diff+xml

      Mandatory parameters: none

      Optional parameters: Same as charset parameter application/xml as
      specified in RFC 3023 [5].

      Encoding considerations: Same as encoding considerations of
      application/xml as specified in RFC 3023 [5].

      Security considerations: See Section 10 of RFC 3023 [5] and
      Section 6 of RFCXXXX [[NOTE TO RFC-EDITOR/IANA: Please replace
      XXXX with the RFC number of this specification.]].

      Interoperability considerations: none.

      Published specification: This document.

      Applications which use this media type: This document type has
      been used to support manipulation of resource lists [14] using
      XCAP.

      Additional Information:

         Magic Number: None

         File Extension: .xdf

         Macintosh file type code: "TEXT"






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         Personal and email address for further information: Jonathan
         Rosenberg, jdrosen@jdrosen.net

         Intended usage: COMMON

         Author/Change controller: The IETF.

7.2.  URN Sub-Namespace Registration for
      urn:ietf:params:xml:ns:xcap-diff

   This section registers a new XML namespace, as per the guidelines in
   [7]

      URI: The URI for this namespace is
      urn:ietf:params:xml:ns:xcap-diff.

      Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org),
      Jonathan Rosenberg (jdrosen@jdrosen.net).

      XML:


              BEGIN
              <?xml version="1.0"?>
              <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                   "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
              <html xmlns="http://www.w3.org/1999/xhtml">
              <head>
                <meta http-equiv="content-type"
                   content="text/html;charset=iso-8859-1"/>
                <title>XCAP Diff Namespace</title>
              </head>
              <body>
                <h1>Namespace for XCAP Diff</h1>
                <h2>urn:ietf:params:xml:ns:xcap-diff</h2>
                <p>See <a href="[URL of published RFC]">RFCXXXX[[NOTE
 TO IANA/RFC-EDITOR: Please replace XXXX with the RFC number of this
 specification.]]</a>.</p>
              </body>
              </html>
              END

7.3.  Schema Registration

   This section registers a new XML schema per the procedures in [7].






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      URI: urn:ietf:params:xml:schema:xcap-diff

      Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org),
      Jonathan Rosenberg (jdrosen@jdrosen.net).

      The XML for this schema can be found as the sole content of
      Section 4.


8.  Acknowledgments

   The authors would like to thank Pavel Dostal, Jeroen van Bemmel,
   Martin Hynar and Anders Lindgren for their valuable comments.


9.  References

9.1.  Normative References

   [1]   "Canonical XML 1.0", W3C Recommendation REC-xml-c14n-20010315 ,
         March 2001.

   [2]   "Extensible Markup Language (XML) 1.0 (Fourth Edition)", W3C
         Recommendation REC-xml-20060816 , August 2006.

   [3]   "Namespaces in XML (Second Edition)", W3C Recommendation REC-
         xml-names-20060816 , August 2006.

   [4]   Moats, R., "URN syntax", RFC 2141, May 1997.

   [5]   Murata, M., "XML media types", RFC 3023, January 2001.

   [6]   Moats, R., "A URN namespace for IETF documents", RFC 2648,
         Aug. 1999.

   [7]   Mealling, M., "The IETF XML Registry", RFC 3688, BCP 81,
         January 2004.

   [8]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

   [9]   Rosenberg, J., "The Extensible Markup Language (XML)
         Configuration Access Protocol (XCAP)", RFC 4825, May 2007.

   [10]  Urpalainen, J., "An Extensible Markup Language (XML) Patch
         Operations Framework Utilizing XML Path Language (XPath)
         Selectors",  draft-ietf-simple-xml-patch-ops-03, August 2007.




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9.2.  Informative References

   [11]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
         Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
         Session Initiation Protocol", RFC 3261, June 2002.

   [12]  Roach, A., "Session Initiation Protocol (SIP)-Specific Event
         Notification", RFC 3265, June 2002.

   [13]  Roach, A., Campbell, B., and J. Rosenberg, "A Session
         Initiation Protocol (SIP) Event Notification Extension for
         Resource Lists", RFC 4662, August 2006.

   [14]  Rosenberg, J., "Extensible Markup Language (XML) Formats for
         Representing Resource Lists", RFC 4826, May 2007.

   [15]  Burger, E., Ed., "A Mechanism for Content Indirection in
         Session Initiation Protocol (SIP) Messages", RFC 4483,
         May 2006.


Authors' Addresses

   Jonathan Rosenberg
   Cisco
   Edison, NJ
   US

   Email: jdrosen@cisco.com
   URI:   http://www.jdrosen.net


   Jari Urpalainen
   Nokia
   Itamerenkatu 11-13
   Helsinki  00180
   Finland

   Phone: +358 7180 37686
   Email: jari.urpalainen@nokia.com











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Internet-Draft              XCAP Diff Format                 August 2007


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