SIMPLE WG M. Lonnfors
Internet-Draft E. Leppanen
Expires: August 25, 2005 Nokia
H. Khartabil
Telio
J. Urpalainen
Nokia Research Center
February 21, 2005
Presence Information Data format (PIDF) Extension for Partial
Presence
draft-ietf-simple-partial-pidf-format-03
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
The Presence Information Document Format (PIDF) specifies the
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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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Structure of partial PIDF 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 Content-type registration for
'application/pidf-diff+xml' . . . . . . . . . . . . . . . 5
5.2 URN sub-namespace registration for
'urn:ietf:params:xml:ns:pidf-diff' . . . . . . . . . . . . 6
5.3 XML Schema Registration . . . . . . . . . . . . . . . . . 7
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . 11
8. Interoperability Considerations . . . . . . . . . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . 12
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 12
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1 Normative references . . . . . . . . . . . . . . . . . . 12
11.2 Informative references . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 13
Intellectual Property and Copyright Statements . . . . . . . 15
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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 'application/pidf-diff+xml'
which enables transporting of only changed parts of the PIDF based
presence information.
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.
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. A document with MIME
type 'application/pidf-diff+xml' represents a partial presence
document.
3. Structure of partial PIDF documents
The mechanism for implementing the partial PIDF requires defining a
new MIME type which is named as 'application/pidf-diff+xml'.
The data format includes XML Schema types described in [7]. The
patch operation elements: <add>, <remove> or <replace> defined
according to the patch operation XML Schema types will allow changing
the fragments of the local copy of the full presence document. As
the names imply the <add> element is used to add new content and
<replace> element is used to update the existing content whereas
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<remove> element is used to remove some content.
In addition to patch operation elements the data format consists of
some additional parameters. The 'version' attribute within the
document root node contains a sequence number that is progressively
incremented by one between subsequent document updates i.e. a more
recent document update has a higher 'version' value than the previous
one. This is used to ensure consistent updates as the recipient of
the document can use the 'version' attribute value to properly order
received documents.
Implementations using this document format must follow guidelines
specified in the PIDF [3]. Specifically, 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 [4], using the namespace identifier 'ietf'
specified in RFC 2648 [5] and extended by RFC3688 [6]. This URN is:
urn:ietf:params:xml:ns:pidf-diff
3.1 'version' attribute
Every presence document compliant with this specification contains a
'version' attribute in the <pidf-diff> element.
3.2 'entity' attribute
Every presence document compliant with this specification MAY contain
an 'entity' attribute in the <pidf-diff> root document node. It's
content MUST then be the same than that of the full presence
document.
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
queued changes it may be desirable to send the full presence document
content instead. How this will be done in practice is beyond the
scope of this document. This document format allows to use the root
node selector i.e. "presence" which actually contains the full
content of the presence document as there can only be one root node
in any valid XML document. It should be noted that it is still
impossible to create a new document with this format, i.e. first the
full presence document has to be sent with the PIDF format and then
only patches are sent with this pidf-diff format.
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5. IANA Considerations
This memo calls for IANA to:
o register a new XML namespace URN per [6].
o register a new content type 'application/pidf-diff+xml' per
RFC2048 [10].
o register a new XML Schema URN per [6].
5.1 Content-type registration for 'application/pidf-diff+xml'
MIME media type name: application
MIME subtype name: pidf-diff+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 [8], 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]]]
Applications which use this media type: SIP-based presence systems
Additional information:
Magic Number: None
File Extension: .xml
Macintosh file type code: "TEXT"
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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-diff'
URI:
urn:ietf:params:xml:ns:pidf-diff
Description:
This is the XML namespace for XML elements defined by
[[[RFCXXXX]]] to describe the 'application/pidf-diff+xml' content
type for partial PIDF.
Registrant Contact:
IETF, SIMPLE working group, <simple@ietf.org>
Mikko Lonnfors, <mikko.lonnfors@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="[[[URL of published RFC]]]">
RFCXXXX</a>.</p>
</body>
</html>
END
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5.3 XML Schema Registration
This section registers a new XML Schema.
URI:
urn:ietf:params:xml:schema:pidf-diff
Registrant Contact:
IETF, SIMPLE working group, <simple@ietf.org>
Mikko Lonnfors, <mikko.lonnfors@nokia.com>
6. Examples
An 'application/pidf+xml' document that contains full state
information:
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:pe="urn:ietf:params:xml:ns:pidf:rpid-person"
xmlns:de="urn:ietf:params:xml:ns:pidf:rpid-device"
xmlns:rs="urn:ietf:params:xml:ns:pidf:status:rpid-status"
xmlns:rt="urn:ietf:params:xml:ns:pidf:rpid-tuple"
xmlns:ci="urn:ietf:params:xml:ns:pidf:cipid"
xmlns:sc="urn:ietf:params:xml:ns:pidf:servcaps"
xmlns:dc="urn:ietf:params:xml:ns:pidf:status:devcaps"
entity="pres:someone@example.com">
<tuple id="sg89ae">
<status>
<basic>open</basic>
<rs:relationship>assistant</rs:relationship>
</status>
<sc:servcaps>
<sc:audio>true</sc:audio>
<sc:video>false</sc:video>
<sc:message>true</sc:message>
</sc: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>
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<tuple id="r1230d">
<status>
<basic>closed</basic>
<rs:activity>meeting</rs:activity>
</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>
<pe:person>
<pe:status>
<rs:activities>
<rs:on-the-phone/>
<rs:busy/>
</rs:activities>
</pe:status>
</pe:person>
<de:device id="urn:esn:600b40c7">
<de:status>
<dc:devcaps>
<dc:mobility>
<dc:supported>
<dc:mobile/>
</dc:supported>
</dc:mobility>
</dc:devcaps>
</de:status>
</de:device>
<note xml:lang="en">Full state presence document</note>
</presence>
An 'application/pidf-diff+xml' document that contains four example
updates:
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<?xml version="1.0" encoding="UTF-8"?>
<pidf-diff xmlns="urn:ietf:params:xml:ns:pidf-diff"
xmlns:p="urn:ietf:params:xml:ns:pidf"
xmlns:pe="urn:ietf:params:xml:ns:pidf:person"
xmlns:rs="urn:ietf:params:xml:ns:pidf:status:rpid-status"
entity="pres:someone@example.com"
version="1">
<add parent="p:presence" sel="*[4]">
<p:tuple id="ert4773">
<p:status>
<p:basic>open</p:basic>
</p:status>
<p:contact priority="0.4">mailto:pep@example.com</p:contact>
<p:note xml:lang="en">This is a new tuple inserted
between the last tuple and person element</p:note>
</p:tuple>
</add>
<replace sel="*/p:tuple[@id='r1230d']/p:status/p:basic/text()"
>open</replace>
<remove sel="*/pe:person/pe:status/rs:activities/rs:busy"/>
<replace sel="*/p:tuple[@id='cg231jcr']/p:contact/@priority"
>0.7</replace>
</pidf-diff>
An updated local composition presence document after applying the
patches:
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:pe="urn:ietf:params:xml:ns:pidf:person"
xmlns:de="urn:ietf:params:xml:ns:pidf:device"
xmlns:rs="urn:ietf:params:xml:ns:pidf:status:rpid-status"
xmlns:rt="urn:ietf:params:xml:ns:pidf:rpid-tuple"
xmlns:ci="urn:ietf:params:xml:ns:pidf:cipid"
xmlns:sc="urn:ietf:params:xml:ns:pidf:servcaps"
xmlns:dc="urn:ietf:params:xml:ns:pidf:status:devcaps"
entity="pres:someone@example.com">
<tuple id="sg89ae">
<status>
<basic>open</basic>
<rs:relationship>assistant</rs:relationship>
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</status>
<sc:servcaps>
<sc:audio>true</sc:audio>
<sc:video>false</sc:video>
<sc:message>true</sc:message>
</sc: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 person element</note>
</tuple>
<pe:person>
<pe:status>
<rs:activities>
<rs:on-the-phone/>
</rs:activities>
</pe:status>
</pe:person>
<de:device id="urn:esn:600b40c7">
<de:status>
<dc:devcaps>
<dc:mobility>
<dc:supported>
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<dc:mobile/>
</dc:supported>
</dc:mobility>
</dc:devcaps>
</de:status>
</de:device>
<note xml:lang="en">Full state presence document</note>
</presence>
7. XML Schema
The XML schema for the 'application/pidf-diff+xml' data format. The
included schema "xcap-patch-opers.xsd" is defined in [7].
<?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:xsd="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
<xsd:include schemaLocation="xcap-patch-ops.xsd"/>
<xsd:element name="pidf-diff">
<xsd:complexType>
<xsd:sequence minOccurs="0" maxOccurs="unbounded">
<xsd:choice>
<xsd:element name="add" type="tns:addType"/>
<xsd:element name="replace" type="tns:replaceType"/>
<xsd:element name="remove" type="tns:removeType"/>
</xsd:choice>
</xsd:sequence>
<xsd:attribute name="entity" type="xsd:anyURI" use="optional"/>
<xsd:attribute name="version" type="xsd:unsignedInt"
use="required"/>
</xsd:complexType>
</xsd:element>
</xsd:schema>
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8. Interoperability Considerations
Systems compliant with CPP [9] 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 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 preserve
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 [3] apply unchanged for this document.
10. Acknowledgments
The authors would like to thank Jose Costa-Requena, Jyrki Aarnos,
Jonathan Rosenberg, Dean Willis, Miguel Garcia, Kriztian Kiss, Ben
Cambell, Robert Sparks, Anders kristenssen and Aki Niemi 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] Sugano, H., "CPIM presence information data format", RFC 3863,
May 2003.
[4] Moats, R., "URN syntax", RFC 2141, May 1997.
[5] Moats, R., "A URN namespace for IETF documents", RFC 2648, Aug.
1999.
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[6] Mealling, M., "The IETF XML Registry", RFC 3688, BCP 81, January
2004.
[7] Urpalainen, J., "The Extensible Markup Language (XML)
Configuration Access Protocol (XCAP) Patch Operations",
draft-urpalainen-simple-xcap-patch-ops-00, February 2005.
11.2 Informative references
[8] Murata, M., "XML media types", RFC 3023, January 2001.
[9] Peterson, J., "Common Profile for Presence (CPP)", RFC 3859.
[10] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet
Mail Extensions (MIME) Part Four: Registration Procedures",
RFC 2048, November 1996.
[11] Rosenberg, J., "A Data Model for Presence",
draft-ietf-simple-presence-data-model-01 (work in progress),
October 2004.
[12] Schulzrinne, H., Gurbani, V., Kyzivat, P. and J. Rosenberg,
"RPID: Rich Presence Extensions to the Presence Information
Data Format (PIDF)", draft-ietf-simple-rpid-04 (work in
progress), October 2004.
[13] Schulzrinne, H., "CIPID: Contact Information in Presence
Information Data Format", draft-ietf-simple-cipid-03 (work in
progress), July 2004.
Authors' Addresses
Mikko Lonnfors
Nokia
Itamerenkatu 11-13 00180
Helsinki
Finland
Phone: +358 71 8008000
Email: mikko.lonnfors@nokia.com
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Eva Leppanen
Nokia
P.O BOX 785
Tampere
Finland
Phone: +358 7180 77066
Email: eva-maria.leppanen@nokia.com
Hisham Khartabil
Telio
P.O. Box 1203 Vika
Oslo
Norway
Phone: +47 2167 3544
Email: hisham.khartabil@telio.no
Jari Urpalainen
Nokia Research Center
Itamerenkatu 11-13 00180
Helsinki
Finland
Phone: +358 7180 37686
Email: jari.urpalainen@nokia.com
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