Network Working Group H. Schulzrinne

Network Working Group H. Schulzrinne
Request for Comments: 4482 Columbia U.
Category: Standards Track July 2006

CIPID: Contact Information for the Presence Information Data Format

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.

Copyright Notice

Copyright (C) The Internet Society (2006).

Abstract

The Presence Information Data Format (PIDF) defines a basic XML
format for presenting presence information for a presentity. The
Contact Information for the Presence Information Data format (CIPID)
is an extension that adds elements to PIDF that provide additional
contact information about a presentity and its contacts, including
references to address book entries and icons.

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RFC 4482 CIPID July 2006

Table of Contents

1. Introduction ....................................................2
2. Terminology and Conventions .....................................3
3. CIPID Elements ..................................................3
3.1. Card Element ...............................................3
3.2. Display-Name Element .......................................3
3.3. Homepage Element ...........................................3
3.4. Icon Element ...............................................4
3.5. Map Element ................................................4
3.6. Sound Element ..............................................4
4. Example .........................................................4
5. The XML Schema Definition .......................................6
6. IANA Considerations .............................................7
6.1. URN Sub-Namespace Registration for .........................7
'urn:ietf:params:xml:ns:pidf:cipid'
6.2. Schema Registration for Schema
'urn:ietf:params:xml:ns:pidf:cipid' ........................7
7. Internationalization Considerations .............................8
8. Security Considerations .........................................8
9. References ......................................................9
9.1. Normative References .......................................9
9.2. Informative References ....................................10

1. Introduction

Presence information facilitates communication; its usefulness can be
enhanced by providing basic information about a presentity or
contact. This specification describes a basic set of information
elements that allow a watcher to retrieve additional information
about a presentity or contact.

This specification defines extensions to the PIDF [9] Extensible
Markup Language [7][8][10] (XML) document format.

We describe elements for providing a "business card", references to
the homepage, map, representative sound, display name, and an icon.
This additional presence information can be used in PIDF [9]
documents, together with Rich Presence Information Data format [11]
(RPID), future-status [12], and other PIDF extensions.

All elements extend the <person> or, less commonly, <tuple> element
in the presence data model [13]. The <tuple> element is only
extended with Contact Information for the Presence Information Data
format (CIPID) elements if the information describes a service
referring to another person that is marked by an RPID <relationship>
element with a value other than 'self'. All elements described in
this document are optional.

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RFC 4482 CIPID July 2006

RPID and CIPID both provide "rich" presence that goes beyond the
basic 'open' and 'closed' status information in PIDF. The presence
information described in these two documents can be supplied
independently, although in practice, both will often appear in the
same PIDF document. CIPID elements describe the more static aspects
of somebody's presence information, while RPID focuses on elements
that will likely change throughout the day. Thus, CIPID information
can often be statically configured by the user through the graphical
user interface of a presence client; this is less likely to be
sufficient for RPID.

The namespace URI for these elements defined by this specification is
a URN [2], using the namespace identifier 'ietf' defined by [4] and
extended by [6]:

urn:ietf:params:xml:ns:pidf:cipid

2. Terminology and Conventions

The key words MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT,
RECOMMENDED, MAY, and OPTIONAL in this document are to be interpreted
as described in BCP 14, RFC 2119 [1].

3. CIPID Elements

Unless otherwise noted below, each element may only appear at most
once.

3.1. Card Element

The <card> element includes a URI pointing to a business card, e.g.,
in LDAP Data Interchange Format [15] (LDIF) or vCard [14] format.

3.2. Display-Name Element

The <display-name> element includes the name identifying the tuple or
person that the presentity suggests should be shown by the watcher
user interface. It is left to the watcher user interface design to
choose whether to heed this suggestion or to use some other suitable
string. The CIPID information MAY contain multiple display names,
but only if they are labeled with different 'xml:lang' attributes.
This allows a Korean-speaking presentity to convey its display name
in different languages, Latin and Hangul, for example.

3.3. Homepage Element

The <homepage> element provides a URI pointing to general information
about the tuple or person, typically a web home page.

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RFC 4482 CIPID July 2006

3.4. Icon Element

The <icon> element provides a URI pointing to an image (icon)
representing the tuple or person. The watcher can use this
information to represent the tuple or person in a graphical user
interface. Presentities SHOULD provide images of sizes and aspect
ratios that are appropriate for rendering as an icon. Support for
JPEG, PNG, and GIF formats is REQUIRED.

3.5. Map Element

The <map> element provides a URI pointing to a map related to the
tuple or person. The watcher can use this information to represent
the tuple or person in a graphical user interface. The map may be
either an image, an HTML client-side image map, or a geographical
information system (GIS) document, e.g., encoded as GML. Support for
images formatted as PNG and GIF is REQUIRED.

3.6. Sound Element

The <sound> element provides a URI pointing to a sound related to the
tuple or person. The watcher MAY use the sound object, such as a
MIDI or MP3 file, referenced by the URL to inform the watcher that
the presentity has assumed the status OPEN. Implementors are advised
to create user interfaces that provide the watcher with the
opportunity to choose whether to play such sounds. Support for
sounds coded as MPEG-2 Layer 3 (MP3) is RECOMMENDED. The sound
object might also be used to indicate how to pronounce the
presentity's name.

4. Example

An example using CIPID only is shown below:

<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
xmlns:c="urn:ietf:params:xml:ns:pidf:cipid"
entity="pres:[email protected]">

<tuple id="bs35r9">
<status>
<basic>open</basic>
</status>
<contact priority="0.8">im:[email protected]</contact>
<timestamp>2005-11-21T16:14:29Z</timestamp>
</tuple>

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RFC 4482 CIPID July 2006

<dm:person id="p1">
<c:card>http://example.com/~alice/card.vcd</c:card>
<c:display-name>Alice Lewis</c:card>
<c:homepage>http://example.com/~alice</c:homepage>
<c:icon>http://example.com/~alice/me.png</c:icon>
<c:map>http://example.com/~alice/gml-map.xml</c:map>
<c:sound>http://example.com/~alice/hello.wav</c:sound>
<dm:timestamp>2005-11-21T09:00:00+05:00</dm:timestamp>
</dm:person>
</presence>

An example combining RPID and CIPID is shown below:

<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
xmlns:c="urn:ietf:params:xml:ns:pidf:cipid"
xmlns:r="urn:ietf:params:xml:ns:pidf:rpid"
xsi:schemaLocation="urn:ietf:params:xml:ns:pidf pidf.xsd
urn:ietf:params:xml:ns:pidf:data-model data-model.xsd
urn:ietf:params:xml:ns:pidf:cipid cipid.xsd
urn:ietf:params:xml:ns:pidf:rpid rpid.xsd"
entity="pres:[email protected]">

<tuple id="bs35r9">
<status>
<basic>open</basic>
</status>
<contact priority="0.8">im:[email protected]</contact>
<timestamp>2005-05-30T22:00:29Z</timestamp>
</tuple>

<tuple id="bs78">
<status>
<basic>closed</basic>
</status>
<r:relationship><r:assistant/></r:relationship>
<c:card>http://example.com/~assistant/card.vcd</c:card>
<c:homepage>http://example.com/~assistant</c:homepage>
<contact priority="0.1">im:[email protected]</contact>
<timestamp>2005-05-30T22:00:29Z</timestamp>
</tuple>

<dm:person id="p1">
<c:card>http://example.com/~someone/card.vcd</c:card>
<c:homepage>http://example.com/~someone</c:homepage>
<c:icon>http://example.com/~someone/icon.gif</c:icon>

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RFC 4482 CIPID July 2006

<c:map>http://example.com/~someone/gml-map.xml</c:map>
<c:sound>http://example.com/~someone/whoosh.wav</c:sound>
<dm:timestamp>2005-05-30T22:02:44+05:00</dm:timestamp>
</dm:person>
</presence>

5. The XML Schema Definition

The schema is shown below.

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

<xs:annotation>
<xs:documentation>
Describes CIPID tuple extensions for PIDF.
</xs:documentation>
</xs:annotation>

<xs:element name="card" type="xs:anyURI"/>
<xs:element name="display-name" type="xs:string"/>
<xs:element name="homepage" type="xs:anyURI"/>
<xs:element name="icon" type="xs:anyURI"/>
<xs:element name="map" type="xs:anyURI"/>
<xs:element name="sound" type="xs:anyURI"/>
</xs:schema>

Figure 1: CIPID schema

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RFC 4482 CIPID July 2006

6. IANA Considerations

This document calls for IANA to register a new XML namespace URN and
schema per [6].

6.1. URN Sub-Namespace Registration for
'urn:ietf:params:xml:ns:pidf:cipid'

URI: urn:ietf:params:xml:ns:pidf:cipid
Description: This is the XML namespace for XML elements defined by
RFC 4482 to describe contact information presence information
extensions for the status element in the PIDF presence document
format in the application/pidf+xml content type.
Registrant Contact: IETF, SIMPLE working group, [email protected];
Henning Schulzrinne, [email protected]
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>CIPID: Contact Information for the Presence Information
Data Format</title>
</head>
<body>
<h1>Namespace for contact information presence extension
(status)</h1>
<h2>urn:ietf:params:xml:ns:pidf:cipid</h2>
<p>See <a href="http://www.rfc-editor.org/rfc/rfc4482.txt">
RFC4482</a>.</p>
</body>
</html>
END

6.2. Schema Registration for Schema 'urn:ietf:params:xml:ns:pidf:cipid'

URI: urn:ietf:params:xml:ns:pidf:cipid
Registrant Contact: IESG
XML: See Figure 1

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7. Internationalization Considerations

CIPID delivers only URLs, except for the <display-name> element. The
resolution of the URLs can negotiate appropriate language and
character sets within the URL-designated protocol.

For the display name and to handle Internationalized Resource
Identifiers (IRIs) [16], since CIPID is represented in XML, it
provides native support for encoding information using the Unicode
character set and its more compact representations including UTF-8.
Conformant XML processors recognize both UTF-8 and UTF-16. Though
XML includes provisions to identify and use other character encodings
through use of an "encoding" attribute in an <?xml?> declaration, use
of UTF-8 is RECOMMENDED in environments where parser encoding support
incompatibility exists.

The XML 'xml:lang' attribute can be used to identify the language and
script for the <display-name> element. The specification allows
multiple occurrences of this element so that the presentity can
convey display names in multiple scripts and languages. If no 'xml:
lang' attribute is provided, the default value is "i-default" [3].

8. Security Considerations

The security issues are similar to those for RPID [11]. Watchers
need to restrict which content types of content pointed to by <icon>,
<homepage>, <map>, <sound>, and <vcard> elements they render.

Also, when a watcher accesses these URIs, the presentity may deduce
that the watcher is currently using the presence application. Thus,
a presence application concerned about leaking this information may
want to cache these objects for later use. (A presentity could
easily customize the URLs for each watcher, so that it can tell who
is referencing the objects.) This caching behavior may cause the
information to become stale, out-of-sync with the current data until
the cache is refreshed. Fortunately, the elements in CIPID are
expected to retain the same content for periods measured in days, so
that privacy-conscious applications may well decide to perform
caching over durations that reveal little current activity
information. Presentities need to keep in mind that clients may
cache the content referenced by URIs for long periods as they use
their presence system to construct presence documents using this
extension. If the referenced content needs to change frequently, the
presentity could, for example, update the presence document with a
new URI to encourage clients to notice.

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RFC 4482 CIPID July 2006

Icons and other URIs in this document could be used as a covert
channel to convey messages to the watcher, outside the content
monitoring that might be in place for instant messages or other
communications channels. Thus, entities that worry about such
channels may want to prohibit the usage of URLs pointing to resources
outside their domain, for example.

Implementors must take care to adhere to the mechanisms for verifying
the identity in the referenced server's certificate against the URI.
For instance, if the URI scheme is https, the requirements of RFC
2818 [5], section 3.1, must be met. In particular, the domain
represented in the URI must match the subjectAltName in the
certificate presented by the referenced server. If this identity
check fails, the referenced content SHOULD NOT be retrieved and MUST
NOT be used.

9. References

9.1. Normative References

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

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

[3] Alvestrand, H., "IETF Policy on Character Sets and Languages",
BCP 18, RFC 2277, January 1998.

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

[5] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

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

[7] Maloney, M., Beech, D., Thompson, H., and N. Mendelsohn, "XML
Schema Part 1: Structures Second Edition", W3C REC REC-
xmlschema-1-20041028, October 2004.

[8] Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes Second
Edition", W3C REC REC-xmlschema-2-20041028, October 2004.

[9] 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 4482 CIPID July 2006

[10] Yergeau, F., Paoli, J., Sperberg-McQueen, C., Bray, T., and E.
Maler, "Extensible Markup Language (XML) 1.0 (Third Edition)",
W3C REC REC-xml-20040204, February 2004.

9.2. Informative References

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

[12] Schulzrinne, H., "Timed Presence Extensions to the Presence
Information Data Format (PIDF) to Indicate Status Information
for Past and Future Time Intervals", RFC 4481, July 2006.

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

[14] Dawson, F. and T. Howes, "vCard MIME Directory Profile", RFC
2426, September 1998.

[15] Good, G., "The LDAP Data Interchange Format (LDIF) - Technical
Specification", RFC 2849, June 2000.

[16] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.

Acknowledgements

This document is based on discussions within the IETF SIMPLE working
group. Spencer Dawkins, Vijay Gurbani, Avshalom Houri, Hisham
Khartabil, Paul Kyzivat, Eva Leppanen, Mikko Lonnfors, Aki Niemi, Jon
Peterson, Jonathan Rosenberg, and Robert Sparks provided helpful
comments.

Author's Address

Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US

Phone: +1 212 939 7004
EMail: [email protected]
URI: http://www.cs.columbia.edu

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RFC 4482 CIPID July 2006

Full Copyright Statement

Copyright (C) The Internet Society (2006).

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