SIMPLE WG M. Lonnfors
Internet-Draft E. Leppanen
Expires: May 18, 2007 Nokia
H. Khartabil
Telio
J. Urpalainen
Nokia Research Center
November 14, 2006
Presence Information Data format (PIDF) Extension for Partial Presence
draft-ietf-simple-partial-pidf-format-08
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Copyright Notice
Copyright (C) The Internet Society (2006).
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 the document always needs
to carry all presence information available for the presentity. In
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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 which enables transporting of either only the changed parts or
the full PIDF based presence information.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Structure of PIDF diff documents . . . . . . . . . . . . . . . 3
3.1. 'version' attribute . . . . . . . . . . . . . . . . . . . 4
3.2. 'entity' attribute . . . . . . . . . . . . . . . . . . . . 5
4. Usage of 'application/pidf-diff+xml' . . . . . . . . . . . . . 5
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 . . . . . . . . . . . . . . . 13
9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
10. Internationalization Considerations . . . . . . . . . . . . . 13
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
12.1. Normative references . . . . . . . . . . . . . . . . . . . 14
12.2. Informative references . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
Intellectual Property and Copyright Statements . . . . . . . . . . 17
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1. Introduction
The Presence Information Document Format (PIDF) [3] specifies the
baseline XML based format for describing presence information. One
of the characteristic 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
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
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.
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The XML Schema imports the PIDF [3] 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 allows using also <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 [8] 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
[9]. Partial notification [16] uses 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 [3]. 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
[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 MAY contain
a 'version' attribute within the <pidf-diff> and <pidf-full> element.
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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 [3]. The usage of this
presentity URI is described in more detail in section 3.1 of [13].
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
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 [12].
o register a new XML Schema URN per [6].
5.1. Content-type registration for 'application/pidf-diff+xml'
Type name: application
Subtype name: pidf-diff+xml
Required 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 [10], 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
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[[[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"
Personal and email address for further information: Jari
Urpalainen, jari.urpalainen@nokia.com
Intended usage: LIMITED USE
Restrictions on usage: Presence [3] based systems.
Author:
This specification is a work item of the IETF SIMPLE working
group, with mailing list address <simple@ietf.org>.
Change controller: IETF.
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>
Jari Urpalainen, <jari.urpalainen@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>urn:ietf:params:xml:ns:pidf-diff</h2>
<p>See <a href="[[[URL of published RFC]]]">
RFCXXXX</a>.</p>
</body>
</html>
END
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>
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">
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<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>
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</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">
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<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>
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<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 [8] and the PIDF Schema "pidf.xsd" is imported from [3].
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<?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 xml-patch-ops type definitions -->
<xsd:include
schemaLocation="urn:ietf:params:xml:schema:xml-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>
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8. Interoperability Considerations
Systems compliant with CPP [11] 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. In
SIMPLE based systems use of this MIME type is negotiated using SIP
content type negotiation mechanism as specified in partial
notification [16].
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
All security considerations identified for PIDF [3] apply unchanged
for this document as presence information may contain highly
sensitive information. In addition, once the partial content is
transformed, a malicious man-in-the-middle may easily mess up the
patching process. The protocol used to distribute this content
SHOULD ensure privacy, message integrity and authentication.
Furthermore, the protocol SHOULD provide access controls which
restrict who can see who else's presence information.
10. Internationalization Considerations
The PIDF [3] format is represented in XML which 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.
11. 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 and Jon
Peterson for their valuable comments and contributions.
12. References
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12.1. 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.
[6] Mealling, M., "The IETF XML Registry", RFC 3688, BCP 81,
January 2004.
[7] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", RFC 4288, BCP 13, Dec. 2005.
[8] Urpalainen, J., "An Extensible Markup Language (XML) Patch
Operations Framework Utilizing XML Path Language (XPath)
Selectors", draft-ietf-simple-xml-patch-ops-02, March 2006.
12.2. Informative references
[9] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[10] Murata, M., "XML media types", RFC 3023, January 2001.
[11] Peterson, J., "Common Profile for Presence (CPP)", RFC 3859.
[12] Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet
Mail Extensions (MIME) Part Four: Registration Procedures",
RFC 2048, November 1996.
[13] Rosenberg, J., "A Data Model for Presence", RFC 4479,
July 2006.
[14] Schulzrinne, H., Gurbani, V., Kyzivat, P., and J. Rosenberg,
"RPID: Rich Presence Extensions to the Presence Information
Data Format (PIDF)", RFC 4480, December 2005.
[15] Schulzrinne, H., "CIPID: Contact Information in Presence
Information Data Format", RFC 4482, July 2006.
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[16] Lonnfors, M., Costa-Requena, J., Leppanen, E., and H.
Khartabil, "Session Initiation Protocol (SIP) extension for
Partial Notification of Presence Information",
draft-ietf-simple-partial-notify-07 (work in progress),
July 2006.
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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
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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