A Model for Presence and Instant Messaging
RFC 2778

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• 03

Network Working Group                                          M. Day
Request for Comments: 2778                                      Lotus
Category: Informational                                  J. Rosenberg
                                                          dynamicsoft
                                                            H. Sugano
                                                              Fujitsu
                                                        February 2000

               A Model for Presence and Instant Messaging

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   This document defines an abstract model for a presence and instant
   messaging system. It defines the various entities involved, defines
   terminology, and outlines the services provided by the system. The
   goal is to provide a common vocabulary for further work on
   requirements for protocols and markup for presence and instant
   messaging.

1. Introduction

   A presence and instant messaging system allows users to subscribe to
   each other and be notified of changes in state, and for users to send
   each other short instant messages. To facilitate development of a
   suite of protocols to provide this service, we believe that it is
   valuable to first develop a model for the system. The model consists
   of the various entities involved, descriptions of the basic functions
   they provide, and most importantly, definition of a vocabulary which
   can be used to facilitate discussion.

   We note that the purpose of this model is to be descriptive and
   universal: we want the model to map reasonably onto all of the
   systems that are informally described as presence or instant
   messaging systems. The model is not intended to be prescriptive or
   achieve interoperability: an element that appears in the model will
   not necessarily be an element of an interoperable protocol, and may
   not even be a good idea.

Day, et al.                  Informational                      [Page 1]
RFC 2778       A Model for Presence and Instant Messaging  February 2000

   In this document, each element of the model appears in upper case
   (e.g., PRESENCE SERVICE). No term in lower case or mixed case is
   intended to be a term of the model.

   The first part of this document is intended as an overview of the
   model.  The overview includes diagrams, and terms are presented in an
   order that is intended to help the reader understand the relationship
   between elements. The second part of the document is the actual
   definition of the model, with terms presented in alphabetical order
   for ease of reference.

   The overview is intended to be helpful but is not definitive; it may
   contain inadvertent differences from the definitions in the model.
   For any such difference, the definition(s) in the model are taken to
   be correct, rather than the explanation(s) in the overview.

2. Overview

   The model is intended to provide a means for understanding,
   comparing, and describing systems that support the services typically
   referred to as presence and instant messaging. It consists of a
   number of named entities that appear, in some form, in existing
   systems. No actual implementation is likely to have every entity of
   the model as a distinct part. Instead, there will almost always be
   parts of the implementation that embody two or more entities of the
   model. However, different implementations may combine entities in
   different ways.

   The model defines two services: a PRESENCE SERVICE and an INSTANT
   MESSAGE SERVICE. The PRESENCE SERVICE serves to accept information,
   store it, and distribute it.  The information stored is
   (unsurprisingly) PRESENCE INFORMATION. The INSTANT MESSAGE SERVICE
   serves to accept and deliver INSTANT MESSAGES to INSTANT INBOXES.

2.1 PRESENCE SERVICE

   The PRESENCE SERVICE has two distinct sets of "clients" (remember,
   these may be combined in an implementation, but treated separately in
   the model).  One set of clients, called PRESENTITIES, provides
   PRESENCE INFORMATION to be stored and distributed.  The other set of
   clients, called WATCHERS, receives PRESENCE INFORMATION from the
   service.

Day, et al.                  Informational                      [Page 2]
RFC 2778       A Model for Presence and Instant Messaging  February 2000

                    +---------------------------+
                    |     PRESENCE SERVICE      |
                    |                           |
                    +---------------------------+
                        ^                 |
                        |                 |
                        |                 v
                 +------------+       +------------+