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  or, less commonly,  element
   in the presence data model [13].  The  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 
   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  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  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  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  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  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  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:

   
   

     
       
         open
       
       im:alice@example.net
       2005-11-21T16:14:29Z
     




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       http://example.com/~alice/card.vcd
       Alice Lewis
       http://example.com/~alice
       http://example.com/~alice/me.png
       http://example.com/~alice/gml-map.xml
       http://example.com/~alice/hello.wav
       2005-11-21T09:00:00+05:00
     
   

   An example combining RPID and CIPID is shown below:

   
   

     
       
         open
       
       im:someone@mobile.example.net
       2005-05-30T22:00:29Z
     

     
       
          closed
       
       
       http://example.com/~assistant/card.vcd
       http://example.com/~assistant
       im:assistant@example.com
       2005-05-30T22:00:29Z
     

     
       http://example.com/~someone/card.vcd
       http://example.com/~someone
       http://example.com/~someone/icon.gif



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RFC 4482                         CIPID                         July 2006


       http://example.com/~someone/gml-map.xml
       http://example.com/~someone/whoosh.wav
       2005-05-30T22:02:44+05:00
     
   

5.  The XML Schema Definition

   The schema is shown below.

   
   

     
       
         Describes CIPID tuple extensions for PIDF.
       
     

     
     
     
     
     
     
   

                          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
    
    
    
       CIPID: Contact Information for the Presence Information
         Data Format
    
    
      

Namespace for contact information presence extension (status)

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

See RFC4482.

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 Schulzrinne Standards Track [Page 7] RFC 4482 CIPID July 2006 7. Internationalization Considerations CIPID delivers only URLs, except for the 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 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 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 , , , , and 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. Schulzrinne Standards Track [Page 8] 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. Schulzrinne Standards Track [Page 9] 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: hgs+simple@cs.columbia.edu URI: http://www.cs.columbia.edu Schulzrinne Standards Track [Page 10] RFC 4482 CIPID July 2006 Full Copyright Statement Copyright (C) The Internet Society (2006). 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. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgement Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Schulzrinne Standards Track [Page 11]