Partial PIDF: Presence Information Data Format (PIDF) Extension for Partial Presence

Network Working Group                                        M. Lonnfors
Request for Comments: 5262                                         Nokia
Category: Standards Track                                    E. Leppanen
                                                              Individual
                                                            H. Khartabil
                                                      Ericsson Australia
                                                           J. Urpalainen
                                                                   Nokia
                                                          September 2008


 Presence Information Data Format (PIDF) Extension for Partial Presence

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   The Presence Information Document Format (PIDF) specifies the
   baseline XML-based format for describing presence information.  One
   of the characteristics of the PIDF is that the document always needs
   to carry all presence information available for the presentity.  In
   some environments where low bandwidth and high latency links can
   exist, it is often beneficial to limit the amount of transported
   information over the network.  This document introduces a new MIME
   type that enables transporting of either only the changed parts or
   the full PIDF-based presence information.

Table of Contents

   1. Introduction ....................................................2
   2. Conventions .....................................................3
   3. Structure of PIDF Diff Documents ................................3
      3.1. 'version' Attribute ........................................4
      3.2. 'entity' Attribute .........................................4
   4. Usage of 'application/pidf-diff+xml' ............................4
   5. IANA Considerations .............................................5
      5.1. URN Sub-Namespace Registration for
           'urn:ietf:params:xml:ns:pidf-diff' .........................5
      5.2. application/pidf-diff+xml MIME Type ........................6
      5.3. XML Schema Registration ....................................7
   6. Examples ........................................................8
   7. XML Schema .....................................................11
   8. Interoperability Considerations ................................12
   9. Security Considerations ........................................13
   10. Internationalization Considerations ...........................13
   11. Error Handling ................................................13
   12. Acknowledgments ...............................................13
   13. References ....................................................13
      13.1. Normative references .....................................13
      13.2. Informative references ...................................14

1.  Introduction

   The Presence Information Document Format (PIDF) [RFC3863] specifies
   the baseline XML-based format for describing presence information.
   One of the characteristics of the PIDF is that the document always
   needs to carry all presence information available for the presentity.
   In some environments where low bandwidth and high latency links can
   exist, it is often beneficial to limit the amount of transported
   information over the network.

   This document introduces a new MIME-Type 'application/pidf-diff+xml',
   which enables transporting of either only the changed parts or the
   full PIDF based presence information.  The root element of the
   document distinguishes whether the partial or full PIDF document
   content was transported.

      Note: With this new MIME-Type, applications can easily negotiate
      the support of partial updates of presence by using the Accept
      header.  If PIDF had initially been designed for partial updates,
      a new separate MIME-Type would have been unnecessary.

2.  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 RFC 2119 [RFC2119] and
   indicate requirement levels for compliant implementations.

   This memo makes use of the vocabulary defined in RFC 2778 [RFC2778].
   In addition, the following terms are defined:

   Full presence document:  A presence document that contains all the
      presentity's presence information that is available to a
      particular watcher.

   Partial presence document:  A presence document that represents a
      fragment of the full presence document.  A partial presence
      document can only be understood in the context of the full
      presence document, i.e., a partial presence document modifies a
      cached copy of the full presence document.

3.  Structure of PIDF Diff Documents

   The MIME type 'application/pidf-diff+xml' defines the new content
   type for partial PIDF documents.

   The XML Schema imports the PIDF [RFC3863] schema so that the full
   PIDF document content with the addition of a 'version' attribute can
   be transported.  The root element of the document is then
   <pidf-full>, and the 'version' attribute information can be included
   within it.  Otherwise, the content of <pidf-full> element is exactly
   the same as what would have been if 'application/pidf+xml' content
   type had been used.  Although the XML Schema also allows using
   <presence> as the document root element, it is disallowed from
   applications utilizing this document format.

   When only the changes of the presence document are transported, the
   model described in XML patch operations [RFC5261] is used.  The root
   element of the document is then <pidf-diff>.  The patch operation
   elements: <add>, <remove>, and <replace> allow changing the partial
   content of the cached local copy of the full presence document.  The
   <add> element is used to add new content, the <replace> element
   updates, and the <remove> element removes existing content.

   The optional 'version' attribute within the two possible document
   root elements contains a sequence number which is incremented by one
   between subsequent document updates, i.e., a more recent document
   update has a higher 'version' value than the previous one.  This
   number can be used to ensure consistent updates as the recipient of
   the document can use the 'version' number to properly order received
   documents and to ensure that updates have not been lost.  The usage
   of this attribute thus allows "state delta" processing described in
   [RFC3265].  Partial notification [RFC5263] uses a similar model.
   This number increments independently regardless of whether the
   <pidf-full> or the <pidf-diff> content is transported.  In other
   words, a single version counter is maintained across <pidf-full> and
   <pidf-diff> documents.

   Implementations using this document format MUST follow guidelines
   specified in the PIDF [RFC3863] and PIDF extension formats, for
   example, DataModel [RFC4479], Rich Presence Information Data (RPID)
   [RFC4480], and Contact Information in PIDF (CIPID) [RFC4482] MUST
   support the usage of the XML schema data type ID
   [W3C.REC-xmlschema-2-20041028] of these listed RFCs.  Specifically,
   the XML document MUST be well formed and SHOULD be valid.  This
   specification makes use of XML namespaces for identifying presence
   documents and document fragments.  The namespace URI for elements
   defined by this specification is a URN [RFC2141], using the namespace
   identifier 'ietf' specified in RFC 2648 [RFC2648] and extended by RFC
   3688 [RFC3688].  This URN is:

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

3.1.  'version' Attribute

   Every presence document compliant with this specification MAY contain
   a 'version' attribute within the <pidf-diff> and <pidf-full> element.

3.2.  'entity' Attribute

   Every presence document compliant with this specification MAY contain
   an 'entity' attribute within the <pidf-diff> element.  Its content, a
   presentity URI, MUST then be the same as the 'entity' attribute value
   of the <presence> element described in [RFC3863].  The usage of this
   presentity URI is described in more detail in Section 3.1 of
   [RFC4479].

4.  Usage of 'application/pidf-diff+xml'

   The partial presence document SHOULD only contain those elements or
   attributes that have changed.  However, when there are a lot of
   changes, the full presence document content can then be transported
   instead.

5.  IANA Considerations

   IANA has performed the following actions:

   o  registered a new XML namespace URN per [RFC3688].

   o  registered a new MIME type 'application/pidf-diff+xml' according
      to the procedures of RFC 4288 [RFC4288] and guidelines in RFC 3023
      [RFC3023].

   o  registered a new XML Schema according to the procedures of RFC
      3688 [RFC3688].

5.1.  URN Sub-Namespace Registration for
      'urn:ietf:params:xml:ns:pidf-diff'

   This specification registers a new XML namespace, as per the
   guidelines in RFC 3688 [RFC3688].

      URI:
      urn:ietf:params:xml:ns:pidf-diff

      Description:
      This is the XML namespace for XML elements defined by RFC 5262 to
      describe the 'application/pidf-diff+xml' content type for partial
      PIDF.

      Registrant Contact:
      IETF, SIMPLE working group, (simple@ietf.org)
      Jari Urpalainen, (jari.urpalainen@nokia.com)
   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>PIDF extension for partial PIDF</title>
     </head>
     <body>
       <h1>Namespace for PIDF extension for partial
           notifications</h1>
       <h2>urn:ietf:params:xml:ns:pidf-diff</h2>
       <p>See <a href="http://www.rfc-editor.org/rfc/rfc5262.txt">
        RFC5262</a>.</p>
     </body>
   </html>
   END

5.2.  application/pidf-diff+xml MIME Type

   MIME media type name: application

   MIME subtype name: pidf-diff+xml

   Mandatory parameters: none

   Optional parameters:
   Same as charset parameter of application/xml as specified in RFC 3023
   [RFC3023].  Default value is UTF-8.

   Encoding considerations:
   Same as encoding considerations of application/xml as specified in
   RFC 3023 [RFC3023].

   Security considerations:
   See Section 10 of RFC 3023 [RFC3023].  This content type is designed
   to carry presence data, which may be considered private information.
   Appropriate precautions should be adopted to limit disclosure of this
   information.

   Interoperability considerations: none

   Published specification: RFC 5262
   Applications that use this media type: SIP-based presence systems

   Additional information:

      Magic Number: None

      File Extension: .xml

      Macintosh file type code: "TEXT"

   Personal and email address for further information: Jari Urpalainen,
   jari.urpalainen@nokia.com

   Intended usage: LIMITED USE

   Restrictions on usage: Presence [RFC3863] based systems.

   Author:
   This specification is a work item of the IETF SIMPLE working group,
   with mailing list address <simple@ietf.org>.

   Author/Change controller: the IETF.

5.3.  XML Schema Registration

   This section calls for IANA to register a new XML Schema, the sole
   content of which can be found in Section 7.

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

      Registrant Contact:
      IETF, SIMPLE working group, <simple@ietf.org>
      Jari Urpalainen, <jari.urpalainen@nokia.com>

6.  Examples

   An 'application/pidf-diff+xml' document that contains the full state
   presence information:

   <?xml version="1.0" encoding="UTF-8"?>
   <p:pidf-full xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:p="urn:ietf:params:xml:ns:pidf-diff"
          xmlns:r="urn:ietf:params:xml:ns:pidf:rpid"
          xmlns:ci="urn:ietf:params:xml:ns:pidf:cipid"
          xmlns:c="urn:ietf:params:xml:ns:pidf:caps"
          xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
          entity="pres:someone@example.com"
          version="567">

    <tuple id="sg89ae">
     <status>
      <basic>open</basic>
     </status>
     <c:servcaps>
      <c:audio>true</c:audio>
      <c:message>true</c:message>
      <c:video>false</c:video>
     </c:servcaps>
     <contact priority="0.8">tel:09012345678</contact>
    </tuple>

    <tuple id="cg231jcr">
     <status>
      <basic>open</basic>
     </status>
     <contact priority="1.0">im:pep@example.com</contact>
    </tuple>

    <tuple id="r1230d">
     <status>
      <basic>closed</basic>
     </status>
     <ci:homepage>http://example.com/~pep/</ci:homepage>
     <ci:icon>http://example.com/~pep/icon.gif</ci:icon>
     <ci:card>http://example.com/~pep/card.vcd</ci:card>
     <contact priority="0.9">sip:pep@example.com</contact>
    </tuple>

    <note xml:lang="en">Full state presence document</note>

    <dm:person id="p123">
     <r:activities>
      <r:on-the-phone/>
      <r:busy/>
     </r:activities>
    </dm:person>
    <dm:device id="u600b40c7">
     <c:devcaps>
      <c:mobility>
       <c:supported>
        <c:mobile/>
       </c:supported>
      </c:mobility>
     </c:devcaps>
     <dm:deviceID>urn:esn:600b40c7</dm:deviceID>
    </dm:device>

   </p:pidf-full>

   An example partial update document with the <pidf-diff> root element:

   <?xml version="1.0" encoding="UTF-8"?>
   <p:pidf-diff
        xmlns="urn:ietf:params:xml:ns:pidf"
        xmlns:p="urn:ietf:params:xml:ns:pidf-diff"
        xmlns:r="urn:ietf:params:xml:ns:pidf:rpid"
        xmlns:d="urn:ietf:params:xml:ns:pidf:data-model"
        entity="pres:someone@example.com"
        version="568">

   <p:add sel="presence/note" pos="before">
    <tuple id="ert4773">
     <status>
      <basic>open</basic>
     </status>
     <contact priority="0.4">mailto:pep@example.com</contact>
     <note xml:lang="en">This is a new tuple inserted
          between the last tuple and person element</note>
    </tuple>
   </p:add>

   <p:replace sel="*/tuple[@id='r1230d']/status/basic/text()"
      >open</p:replace>

   <p:remove sel="*/d:person/r:activities/r:busy" ws="after"/>

   <p:replace sel="*/tuple[@id='cg231jcr']/contact/@priority"
      >0.7</p:replace>

   </p:pidf-diff>
   An updated local composition presence document after applying the
   patches:

   <?xml version="1.0" encoding="UTF-8"?>
   <p:pidf-full xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:p="urn:ietf:params:xml:ns:pidf-diff"
          xmlns:r="urn:ietf:params:xml:ns:pidf:rpid"
          xmlns:ci="urn:ietf:params:xml:ns:pidf:cipid"
          xmlns:c="urn:ietf:params:xml:ns:pidf:caps"
          xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
          entity="pres:someone@example.com"
          version="568">

    <tuple id="sg89ae">
     <status>
      <basic>open</basic>
     </status>
     <c:servcaps>
      <c:audio>true</c:audio>
      <c:message>true</c:message>
      <c:video>false</c:video>
     </c:servcaps>
     <contact priority="0.8">tel:09012345678</contact>
    </tuple>

    <tuple id="cg231jcr">
     <status>
      <basic>open</basic>
     </status>
     <contact priority="0.7">im:pep@example.com</contact>
    </tuple>

    <tuple id="r1230d">
     <status>
      <basic>open</basic>
     </status>
     <ci:homepage>http://example.com/~pep/</ci:homepage>
     <ci:icon>http://example.com/~pep/icon.gif</ci:icon>
     <ci:card>http://example.com/~pep/card.vcd</ci:card>
     <contact priority="0.9">sip:pep@example.com</contact>
    </tuple>

    <tuple id="ert4773">
     <status>
      <basic>open</basic>
     </status>
     <contact priority="0.4">mailto:pep@example.com</contact>
     <note xml:lang="en">This is a new tuple inserted
         between the last tuple and note element</note>
    </tuple>

    <note xml:lang="en">Full state presence document</note>

    <dm:person id="p123">
     <r:activities>
      <r:on-the-phone/>
     </r:activities>
    </dm:person>

    <dm:device id="u600b40c7">
     <c:devcaps>
      <c:mobility>
       <c:supported>
        <c:mobile/>
       </c:supported>
      </c:mobility>
     </c:devcaps>
     <dm:deviceID>urn:esn:600b40c7</dm:deviceID>
    </dm:device>

   </p:pidf-full>

7.  XML Schema

   The XML schema for the 'application/pidf-diff+xml' data format.  The
   included schema "urn:ietf:params:xml:schema:xml-patch-ops" is defined
   in [RFC5261], and the PIDF Schema "pidf.xsd" is imported from
   [RFC3863].

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

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

    <!-- import PIDF definitions -->
    <xsd:import namespace="urn:ietf:params:xml:ns:pidf"
                schemaLocation="pidf.xsd"/>

    <!-- partial updates -->
    <xsd:element name="pidf-diff">
     <xsd:complexType>
      <xsd:sequence minOccurs="0" maxOccurs="unbounded">
       <xsd:choice>
        <xsd:element name="add" type="tns:add"/>
        <xsd:element name="replace" type="tns:replace"/>
        <xsd:element name="remove" type="tns:remove"/>
       </xsd:choice>
      </xsd:sequence>
      <xsd:attribute name="version" type="xsd:unsignedInt"/>
      <xsd:attribute name="entity" type="xsd:anyURI"/>
     </xsd:complexType>
    </xsd:element>

    <!-- full PIDF in addition to optional version -->
    <xsd:element name="pidf-full">
     <xsd:complexType>
      <xsd:complexContent>
       <xsd:extension base="pidf:presence">
        <xsd:attribute name="version" type="xsd:unsignedInt"/>
       </xsd:extension>
      </xsd:complexContent>
     </xsd:complexType>
    </xsd:element>

   </xsd:schema>

8.  Interoperability Considerations

   Systems compliant with Common Profile for Presence (CPP) [RFC3859]
   will not be by default able to use this specification.  However, this
   will not cause any interoperability problems because all endpoints
   and gateways must support the default MIME type
   (application/pidf+xml) regardless of if they support this
   specification.  Thus, if a gateway or another end point does not
   understand this specification it will not be used.  In SIMPLE-based
   systems, use of this MIME type is negotiated using SIP content type
   negotiation mechanism as specified in partial notification [RFC5263].

   Other CPP-compliant (other than SIP-based) systems can also support
   this specification if they have a mechanism to indicate support for
   it.  If they do, it is possible to build a gateway that will preserve
   end-to-end integrity with usage of partial PIDF.

9.  Security Considerations

   All security considerations identified for PIDF [RFC3863] apply
   unchanged for this document as presence information may contain
   highly sensitive information.  Furthermore, the protocol SHOULD
   provide authorization policies what presence information can be given
   to which watchers, and when, see [RFC5025].

10.  Internationalization Considerations

   The PIDF [RFC3863] format is represented in XML that performs all
   character processing in terms of the Universal Character Set (UCS).
   Conformant XML processors MUST support both UTF-8 and UTF-16
   encodings of the UCS.  UTF-8 is the RECOMMENDED encoding of this
   partial presence format.

   If the character set of the initial <pidf-full> document has been
   accepted by a receiving application, it MUST continue to accept the
   same character set with the subsequent <pidf-diff> documents.
   However, it MUST NOT need to accept a possible character set change.

11.  Error Handling

   Error conditions MAY be indicated by errors defined in [RFC5261].
   This document doesn't define any additional error elements.  If the
   'version' or 'entity' attributes have incorrect content, it MAY be
   indicated by the <invalid-attribute-value> error element.

12.  Acknowledgments

   The authors would like to thank Jose Costa-Requena, Jyrki Aarnos,
   Jonathan Rosenberg, Dean Willis, Miguel Garcia, Krisztian Kiss, Ben
   Cambell, Robert Sparks, Anders Kristenssen, Aki Niemi, Jon Peterson,
   Gonzalo Camarillo, Lars Eggert, Lakshminath Dondeti, and Chris Newman
   for their valuable comments and contributions.

13.  References

13.1.  Normative references

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3863]  Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr,
              W., and J. Peterson, "Presence Information Data Format
              (PIDF)", RFC 3863, August 2004.

   [RFC2141]  Moats, R., "URN Syntax", RFC 2141, May 1997.

   [RFC2648]  Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
              August 1999.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              January 2004.

   [RFC3023]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media
              Types", RFC 3023, January 2001.

   [RFC4288]  Freed, N. and J. Klensin, "Media Type Specifications and
              Registration Procedures", BCP 13, RFC 4288, December 2005.

   [RFC4479]  Rosenberg, J., "A Data Model for Presence", RFC 4479, July
              2006.

   [RFC4480]  Schulzrinne, H., Gurbani, V., Kyzivat, P., and J.
              Rosenberg, "RPID: Rich Presence Extensions to the Presence
              Information Data Format (PIDF)", RFC 4480, July 2006.

   [RFC4482]  Schulzrinne, H., "CIPID: Contact Information for the
              Presence Information Data Format", RFC 4482, July 2006.

   [RFC5261]  Urpalainen, J., "An Extensible Markup Language (XML) Patch
              Operations Framework Utilizing XML Path Language (XPath)
              Selectors", RFC 5261, September 2008.

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

13.2.  Informative references

   [RFC2778]  Day, M., Rosenberg, J., and H. Sugano, "A Model for
              Presence and Instant Messaging", RFC 2778, February 2000.

   [RFC3265]  Roach, A., "Session Initiation Protocol (SIP)-Specific
              Event Notification", RFC 3265, June 2002.

   [RFC3859]  Peterson, J., "Common Profile for Presence (CPP)", RFC
              3859, August 2004.

   [RFC5025]  Rosenberg, J., "Presence Authorization Rules", RFC 5025,
              December 2007.

   [RFC5263]  Lonnfors, M., "Session Initiation Protocol (SIP) Extension
              for Partial Notification of Presence Information", RFC
              5263, September 2008.

Authors' Addresses

   Mikko Lonnfors
   Nokia
   Itamerenkatu 11-13 00180
   Helsinki
   Finland

   Phone: +358 71 8008000
   EMail: mikko.lonnfors@nokia.com


   Eva Leppanen
   Individual
   Lempaala
   Finland

   EMail: eva.leppanen@saunalahti.fi


   Hisham Khartabil
   Ericsson Australia
   P.O. Box 256c
   Melbourne, VIC 3001
   Australia

   EMail: hisham.khartabil@gmail.com


   Jari Urpalainen
   Nokia
   Itamerenkatu 11-13 00180
   Helsinki
   Finland

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

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