A Data Model for Presence
RFC 4479

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Network Working Group                                       J. Rosenberg
Request for Comments: 4479                                 Cisco Systems
Category: Standards Track                                      July 2006

                       A Data Model for 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.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document defines the underlying presence data model used by
   Session Initiation Protocol (SIP) for Instant Messaging and Presence
   Leveraging Extensions (SIMPLE) presence agents.  The data model
   provides guidance on how to map various communications systems into
   presence documents in a consistent fashion.

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RFC 4479                  Presence Data Model                  July 2006

Table of Contents

   1. Introduction ....................................................2
   2. Definitions .....................................................3
   3. The Model .......................................................5
      3.1. Presentity URI .............................................6
      3.2. Person .....................................................7
      3.3. Service ....................................................8
           3.3.1. Characteristics .....................................9
           3.3.2. Reach Information ..................................10
           3.3.3. Relative Information ...............................13
           3.3.4. Status .............................................13
      3.4. Device ....................................................15
      3.5. Modeling Ambiguity ........................................17
      3.6. The Meaning of Nothing ....................................19
      3.7. Status vs. Characteristics ................................19
      3.8. Presence Document Properties ..............................20
   4. Motivation for the Model .......................................21
   5. Encoding .......................................................22
      5.1. XML Schemas ...............................................24
           5.1.1. Common Schema ......................................24
           5.1.2. Data Model .........................................25
   6. Extending the Presence Model ...................................26
   7. Example Presence Document ......................................26
      7.1. Basic IM Client ...........................................27
   8. Security Considerations ........................................29
   9. Internationalization Considerations ............................29
   10. IANA Considerations ...........................................30
      10.1. URN Sub-Namespace Registration ...........................30
      10.2. XML Schema Registrations .................................31
           10.2.1. Common Schema .....................................31
           10.2.2. Data Model ........................................31
   11. Acknowledgements ..............................................31
   12. References ....................................................32
      12.1. Normative References .....................................32
      12.2. Informative References ...................................32

1.  Introduction

   Presence conveys the ability and willingness of a user to communicate
   across a set of devices.  RFC 2778 [10] defines a model and
   terminology for describing systems that provide presence information.
   RFC 3863 [1] defines an XML [5] [6] [7] document format for
   representing presence information.  In these specifications, presence
   information is modeled as a series of tuples, each of which contains
   a status, communications address, and other markup.  However, neither
   specification gives guidance on exactly what a tuple is meant to
   model, or how to map real-world communications systems (and in

Rosenberg                   Standards Track                     [Page 2]
RFC 4479                  Presence Data Model                  July 2006

   particular, those built around the Session Initiation Protocol (SIP)
   [11]) into a presence document.

   In particular, several important concepts are not clearly modeled or
   well delineated by RFCs 2778 and 3863.  These are the following:

   Service:  A communications service, such as instant messaging (IM) or
      telephony, is a system for interaction between users that provides
      certain modalities or content.

   Device:  A communications device is a physical component that a user