    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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    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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       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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    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:someone@example.com">

         <tuple id="bs35r9">
           <status>
             <basic>open</basic>
           </status>
           <contact priority="0.8">im:alice@example.net</contact>
           <timestamp>2005-11-21T16:14:29Z</timestamp>
         </tuple>

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         <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:someone@example.com">

         <tuple id="bs35r9">
           <status>
             <basic>open</basic>
           </status>
           <contact priority="0.8">im:someone@mobile.example.net</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:assistant@example.com</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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           <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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    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, simple@ietf.org;
          Henning Schulzrinne, hgs@cs.columbia.edu
       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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       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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       [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: hgs+simple@cs.columbia.edu
       URI:   http://www.cs.columbia.edu

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       Copyright (C) The Internet Society (2006).

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