Network Working Group M. Lonnfors

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.

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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.

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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

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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.

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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, ([email protected])
Jari Urpalainen, ([email protected])

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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

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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,
[email protected]

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 <[email protected]>.

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, <[email protected]>
Jari Urpalainen, <[email protected]>

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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:[email protected]"
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:[email protected]</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:[email protected]</contact>
</tuple>

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

<dm:person id="p123">
<r:activities>

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<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:[email protected]"
version="568">

<p:add sel="presence/note" pos="before">
<tuple id="ert4773">
<status>
<basic>open</basic>
</status>
<contact priority="0.4">mailto:[email protected]</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>

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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:[email protected]"
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:[email protected]</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:[email protected]</contact>
</tuple>

<tuple id="ert4773">
<status>
<basic>open</basic>
</status>
<contact priority="0.4">mailto:[email protected]</contact>

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<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">


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


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

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<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>


<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.

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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.

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RFC 5262 Partial PIDF September 2008

[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.

Lonnfors, et al. Standards Track [Page 14]

RFC 5262 Partial PIDF September 2008

[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: [email protected]

Eva Leppanen
Individual
Lempaala
Finland

EMail: [email protected]

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

EMail: [email protected]

Jari Urpalainen
Nokia
Itamerenkatu 11-13 00180
Helsinki
Finland

Phone: +358 7180 37686
EMail: [email protected]

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Full Copyright Statement

Copyright (C) The IETF Trust (2008).

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.

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Lonnfors, et al. Standards Track [Page 16]