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Versions: 00 01 02 03 04 05 06 07 08 09 10 RFC 5262

SIMPLE WG                                                    M. Lonnfors
Internet-Draft                                               E. Leppanen
Expires: October 19, 2004                                   H. Khartabil
                                                                   Nokia
                                                          April 20, 2004


     Presence Information Data format (PIDF) Extension for Partial
                                Presence
                draft-ietf-simple-partial-pidf-format-01

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   and any of which I become aware will be disclosed, in accordance with
   RFC 3668.

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   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on October 19, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2004). All Rights Reserved.

Abstract

   The presence Information Document Format (PIDF) specifies the
   baseline XML based format for describing presence information. One of
   the characteristic of the PIDF is that 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 information that is
   transported over the network. This document introduces a new MIME
   type which enables transporting of only changed parts of the PIDF



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   based presence information.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Structure of partial PIDF documents  . . . . . . . . . . . . .  4
     3.1   "version" attribute  . . . . . . . . . . . . . . . . . . .  4
     3.2   "state" attribute  . . . . . . . . . . . . . . . . . . . .  4
     3.3   <removed> element  . . . . . . . . . . . . . . . . . . . .  5
       3.3.1   <t_id> element . . . . . . . . . . . . . . . . . . . .  5
   4.  Usage of 'application/pidf-partial+xml'  . . . . . . . . . . .  5
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  6
     5.1   Content-type registration for
           'application/pidf-partial+xml' . . . . . . . . . . . . . .  6
     5.2   URN sub-namespace registration for
           'urn:ietf:params:xml:ns:pidf-partial'  . . . . . . . . . .  7
   6.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   7.  XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   8.  Interoperability Considerations  . . . . . . . . . . . . . . . 11
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   10.   Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
   11.   References . . . . . . . . . . . . . . . . . . . . . . . . . 12
   11.1  Normative references . . . . . . . . . . . . . . . . . . . . 12
   11.2  Informative references . . . . . . . . . . . . . . . . . . . 12
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 13
       Intellectual Property and Copyright Statements . . . . . . . . 14
























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1.  Introduction

   The presence Information Document Format (PIDF) specifies the
   baseline XML based format for describing presence information. One of
   the characteristic of the PIDF is that 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 information that is
   transported over the network. This document introduces a new MIME
   type which enables transporting of only changed parts of the PIDF
   based presence information.

   This new MIME type works at the <tuple> element level so that it
   allows indicating if new tuples have been added, previously received
   tuples have changed, or that some tuples have been removed. These
   modifications are always relative to previously received presence
   information.

   This document introduces a new MIME-Type 'application/
   pidf-partial+xml' which is based on the PIDF presence data format [4]
   but is enhanced to support partial presence documents.

2.  Conventions

   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 [1] and
   indicate requirement levels for compliant implementations.

   This memo makes use of the vocabulary defined in RFC2778 [2]. 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. A full presence document can be encoded
      according to the MIME type 'application/pidf+xml' or, if the
      "state" attribute is set to "full", it can also be encoded
      according to the MIME type 'application/pidf-partial+xml'.

   Partial presence document: A presence document that represents a
      fragment of the full presence document. A partial presence
      documents can only be understood in the context of the full
      presence document, i.e., a partial presence document modifies a
      local copy of the full presence document. The MIME type
      'application/pidf-partial+xml" document represent a partial
      presence document when the "state" attribute is set to "partial".





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3.  Structure of partial PIDF documents

   The mechanism for implementing the partial PIDF requires defining a
   new MIME type. The new MIME type is named as 'application/
   pidf-partial+xml'. It is similar to the 'application/pidf+xml' [4]
   except that it adds new XML attributes to the <presence> element in
   order to enable the partial PIDF. These new XML attributes are
   "version" and "state". The new MIME type also introduces a new XML
   "removed" element.

   Implementations using this document format must follow guidelines
   specified in the CPIM presence information data format [4] i.e. the
   XML document MUST be well formed and SHOULD be valid. Presence
   documents MUST be based on XML 1.0 and MUST be encoded using UTF-8.
   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 [5], using the
   namespace identifier 'ietf' specified in RFC 2648 [6] and extended by
   RFC3688 [7]. This URN is:

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

3.1  "version" attribute

   Every presence document compliant with this specification MUST
   include the "version" attribute in <presence> element.

   The "version" attribute contains a sequence number that is
   progressively incremented between subsequent documents i.e. a more
   recent document has higher "version" value than a previous one. The
   recipient of the document can use "version" attribute to properly
   order received documents. The version starts with value 0, and is
   incremented by one for each new document. Implementations MUST
   support a 32 bit integer in the version number.

3.2  "state" attribute

   Every presence document compliant with this specification MUST
   include a "state" attribute in the <presence> element. the "state"
   attribute can be set to values: 'full' or 'partial'.

   The "state" attribute indicates the nature of the presence
   information included in the document, i.e., whether it contains a
   full or a partial state corresponding to the cases when the full
   presence information or only changed parts of the presence
   information are delivered. The use of these attributes is similar to
   the watcher information template package [8].




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3.3  <removed> element

   This element is used to carry a list of tuples that are no longer
   present in the presence document. The <removed> element may contain
   any number of <t_id> elements, each of which has the value of the
   "id" attribute of the tuple which has been removed. The <removed>
   element has only semantics for partial presence documents, thus, the
   <removed> element MUST NOT be included if "state" attribute has value
   "full".

3.3.1  <t_id> element

   If a presence document contains a <removed> element, then it MUST
   contain at least one <t_id> element. This element contains the tuple
   ID as indicated by the "id" attribute of the tuple that has been
   removed.

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

   Presence documents which are compliant with the 'application/
   pidf-partial+xml' MIME type MUST be constructed according to
   following logic:

   o  All tuple ids used in the presence document MUST be unique within
      a document. This means tuple ids both in <tuple> elements and in
      <t_id> elements.

   o  If the presence document represents the full presence state the
      "state" attribute MUST be set to "full" and the "version"
      attribute MUST be set to the value 0. The rest of the presence
      document is constructed as defined in the PIDF [4]. A presence
      document that contains a full presence state MUST not contain
      <removed> element.

   o  If the presence document represents a partial presence state the
      "state" attribute MUST be set to "partial". The presence document
      SHOULD only contain those tuples that have changed compared to
      last time the presence document was delivered, i.e., the presence
      document contains new, modified, and  removed tuples. Once a tuple
      is included in the presence document, the whole tuple including
      all the child elements and attributes MUST be included.
      Implementations MUST NOT include a partial tuple. Tuples which
      have not changed SHOULD NOT be included. If some tuples have been
      removed "id" attributes of those tuples MUST be listed using
      <t_id> elements under <removed> element.

   Within the scope of this document tuples are considered to be atomic
   data elements. This means that if a presence document contains an



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   update to an existing tuple, the whole new tuple replaces the old
   one. Partial presence documents can only indicate changes in tuples
   (a tuple is new, modified, removed), since this are the only elements
   that contains identities to refer to. Other child elements to the
   <presence> element defined in the PIDF [4] or in its extensions  MUST
   always be included in partial presence document with its updated
   value, unless the element is removed from the presence information.

5.  IANA Considerations

   This memo calls for IANA to:

   o  register a new XML namespace URN per [7].

   o  register new a content type 'application/pidf-partial+xml' per
      RFC2048 [11].


5.1   Content-type registration for 'application/pidf-partial+xml'

      MIME media type name: application

      MIME subtype name: pidf-partial+xml

      Mandatory parameters: none

      Optional parameters:   charset
      Indicates the character encoding of enclosed XML. Default is
      UTF-8.

      Encoding considerations:
      Uses XML, which can employ 8-bit characters, depending on the
      character encoding used. See RFC 3023 [9], section 3.2.

      Security considerations:
      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. Please refer to
      [[[RFCXXXX]]] security considerations section for more
      information.

      Interoperability considerations: none

      Published specification: [[[RFCXXXX]]] this document

      Applications which use this media type: SIP-based presence systems

      Additional information:



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         Magic Number: None

         File Extension: .xml

         Macintosh file type code: "TEXT"

      Personal and email address for further information: Mikko
      Lonnfors, mikko.lonnfors@nokia.com

      Intended usage: LIMITED USE

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


5.2  URN sub-namespace registration for
    'urn:ietf:params:xml:ns:pidf-partial'

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

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

      Registrant Contact:
      IETF, SIMPLE working group, <simple@ietf.org>
      Mikko Lonnfors, <mikko.lonnfors@nokia.com>

   XML:



















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     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>application/pidf-partial+xml</h2>
             <p>See <a href="[[[URL of published RFC]]]">
             RFCXXXX</a>.</p>
          </body>
          </html>
     END


6.  Examples

   An 'application/pidf-partial+xml' document that contains full state
   information:


























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            <?xml version="1.0" encoding="UTF-8"?>
            <pidf-part:presence xmlns="urn:ietf:params:xml:ns:pidf"
                xmlns:pidf-part="urn:ietf:params:xml:ns:pidf-partial"
                entity="pres:someone@example.com" version="0"
                state="full">

              <tuple id="sg89ae">
                <status><basic>open</basic>
                </status>
                <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>
                <contact priority="0.9">
                      sip:pep@example.com</contact>
              </tuple>
              <note  xml:lang="en">
                Full state presence document
              </note>
             </pidf-part:presence>

    An updated 'application/pidf-partial+xml' document that contains
   partial state information:



















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            <?xml version="1.0" encoding="UTF-8"?>
            <pidf-part:presence xmlns="urn:ietf:params:xml:ns:pidf"
                xmlns:pidf-part="urn:ietf:params:xml:ns:pidf-partial"
               entity="pres:someone@example.com" version="1"
               state="partial">

              <tuple id="cg231jcr">
                <status><basic>closed</basic>
                </status>
                <contact priority="1.0">
                      im:pep@example.com</contact>
                <note xml:lang="en">This is an update of existing
                tuple sent in previous notification</note>
              </tuple>

              <tuple id="wsqw798jcr">
                <status><basic>open</basic>
                </status>
                <contact priority="0.4">
                      im:mac@hut.com</contact>
                <note xml:lang="en">This is a completely new
                tuple not sent in previous notification</note>
              </tuple>
              <note xml:lang="en">
                  Partial state presence document
              </note>
              <pidf-part:removed><pidf-part:t_id>r1230d</pidf-part:t_id>
              </pidf-part:removed>

            </pidf-part:presence>



7.  XML Schema

   The XML schema for the 'application/pidf-partial+xml' data format.


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

        <!-- This import brings in the XML language attribute
          xml:lang-->



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        <xs:import namespace="http://www.w3.org/XML/1998/namespace"
                schemaLocation="http://www.w3.org/2001/xml.xsd"/>
        <xs:import namespace="urn:ietf:params:xml:ns:pidf"/>

        <xs:element name="presence"
         type="tns:partial-presence"/>
        <xs:complexType name="partial-presence">
         <xs:complexContent>
          <xs:extension base="pidf:presence">
           <xs:sequence>
            <xs:element name="removed"
                 type="tns:removed_tuple"
                 minOccurs="0"/>
            </xs:sequence>
            <xs:attribute name="version"
                 type="xs:nonNegativeInteger"
                 use="required"/>
            <xs:attribute name="state" use="required">
            <xs:simpleType>
                 <xs:restriction base="xs:string">
                    <xs:enumeration value="full"/>
                    <xs:enumeration value="partial"/>
                 </xs:restriction>
             </xs:simpleType>
                </xs:attribute>
           </xs:extension>
         </xs:complexContent>
        </xs:complexType>

        <xs:complexType name="removed_tuple">
          <xs:sequence>
            <xs:element name="t_id"
             type="xs:ID"
             minOccurs="1"
             maxOccurs="unbounded"/>
          </xs:sequence>
       </xs:complexType>
   </xs:schema>


8.  Interoperability Considerations

   This specification is not by default compliant with work done in IMPP
   working group. This means that other systems compliant with CPP [10]
   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 if they support this specification. Thus if a



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   gateway or another end point does not understand this specification
   it will not be used.

   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 which will preserves
   the end to end integrity with usage of partial PIDF.

9.  Security Considerations

   Presence information may contain highly sensitive information about
   the presentities. The protocol used to distribute it SHOULD ensure
   privacy, message integrity and authentication. Furthermore, the
   protocol should provide access controls which restrict who can see
   who else's presence information. All security considerations
   identified for PIDF [4] apply unchanged for this document.

10.  Acknowledgements

   The authors would like to thank Jose Costa-Requena, Jyrki Aarnos,
   Jonathan Rosenberg, Dean Willis, Miguel Garcia, Kriztian Kiss, Ben
   Cambell, and Anders kristenssen for their valuable comments and
   contributions.

11.  References

11.1  Normative references

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

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

   [3]  Rosenberg, J., "SIP Extensions for Presence",
        draft-ietf-simple-presence-10 (work in progress), January 2003.

   [4]  Sugano, H., "CPIM presence information data format",
        draft-ietf-impp-cpim-pidf-08 (work in progress), May 2003.

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

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

11.2  Informative references

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



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         January 2004.

   [8]   Rosenberg, J., "A Watcher Information Event Template-Package
         for the Session Initiation Protocol (SIP)",
         draft-ietf-simple-winfo-package-05 (work in progress), January
         2003.

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

   [10]  Crocker, D. and J. Peterson, "Common Profile for Presence
         (CPP)",  draft-ietf-impp-pres-02.txt (work in progress).

   [11]  Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet
         Mail Extensions (MIME) Part Four: Registration Procedures", RFC
         2048, November 1996.


Authors' Addresses

   Mikko Lonnfors
   Nokia
   Itamerenkatu 11-13 00180
   Helsinki
   Finland

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


   Eva Leppanen
   Nokia
   P.O BOX 785
   Tampere
   Finland

   Phone: +358 7180 77066
   EMail: eva-maria.leppanen@nokia.com


   Hisham Khartabil
   Nokia
   P.O. Box 321
   Helsinki
   Finland

   Phone: +358 7180 76161
   EMail: hisham.khartabil@nokia.com




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Intellectual Property Statement

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   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
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   this standard. Please address the information to the IETF at
   ietf-ipr@ietf.org.


Disclaimer of Validity

   This document and the information contained herein are provided on an
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   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Copyright Statement

   Copyright (C) The Internet Society (2004). This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.


Acknowledgment

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




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