1. Terminology

   The following terms are defined in [RFC2778] and are used with those
   definitions in this document:

   ACCESS RULES
   CLOSED
   FETCHER
   INSTANT INBOX
   INSTANT MESSAGE
   NOTIFICATION
   OPEN
   POLLER
   PRESENCE INFORMATION
   PRESENCE SERVICE
   PRESENTITY
   PRINCIPAL
   PROXY
   SERVER
   STATUS
   SUBSCRIBER
   SUBSCRIPTION
   WATCHER

   The terms MUST and SHOULD are used in the following sense while
   specifying requirements:

   MUST: A proposed solution will have to meet this requirement.
   SHOULD: A proposed solution may choose not to meet this requirement.

   Note that this usage of MUST and SHOULD differs from that of RFC
   2119.

   Additionally, the following terms are used in this document and
   defined here:

   ADMINISTRATOR: A PRINCIPAL with authority over local computer and
   network resources, who manages local DOMAINS or FIREWALLS. For
   security and other purposes, an ADMINISTRATOR often needs or wants to
   impose restrictions on network usage based on traffic type, content,
   volume, or endpoints. A PRINCIPAL's ADMINISTRATOR has authority over
   some or all of that PRINCIPAL's computer and network resources.

   DOMAIN: A portion of a NAMESPACE.

   ENTITY: Any of PRESENTITY, SUBSCRIBER, FETCHER, POLLER, or WATCHER
   (all defined in [RFC2778]).

   FIREWALL: A point of administrative control over connectivity.
   Depending on the policies being enforced, parties may need to take
   unusual measures to establish communications through the FIREWALL.

   IDENTIFIER: A means of indicating a point of contact, intended for
   public use such as on a business card. Telephone numbers, email
   addresses, and typical home page URLs are all examples of IDENTIFIERS
   in other systems.  Numeric IP addresses like 10.0.0.26 are not, and
   neither are URLs containing numerous CGI parameters or long arbitrary
   identifiers.

   INTENDED RECIPIENT: The PRINCIPAL to whom the sender of an INSTANT
   MESSAGE is sending it.

   NAMESPACE: The system that maps from a name of an ENTITY to the
   concrete implementation of that ENTITY. A NAMESPACE may be composed
   of a number of distinct DOMAINS.

   OUT OF CONTACT: A situation in which some ENTITY and the PRESENCE
   SERVICE cannot communicate.

   SUCCESSFUL DELIVERY: A situation in which an INSTANT MESSAGE was
   transmitted to an INSTANT INBOX for the INTENDED RECIPIENT, and the
   INSTANT INBOX acknowledged its receipt. SUCCESSFUL DELIVERY usually
   also implies that an INBOX USER AGENT has handled the message in a
   way chosen by the PRINCIPAL. However, SUCCESSFUL DELIVERY does not
   imply that the message was actually seen by that PRINCIPAL.