For
instant messaging
Instant messaging (IM) technology is a type of online chat allowing real-time text transmission over the Internet or another computer network. Messages are typically transmitted between two or more parties, when each user inputs text and trigge ...
, a
presence information watcher is an
entity
An entity is something that exists as itself, as a subject or as an object, actually or potentially, concretely or abstractly, physically or not. It need not be of material existence. In particular, abstractions and legal fictions are usually ...
that requests presence information about a
presentity
The term presentity is a combination of two words - " presence" and "entity". It basically refers to an entity that has presence information associated with it; information such as status, reachability, and willingness to communicate.
Usage
The t ...
from a
presence service Presence service is a network service which accepts, stores and distributes presence information.
Presence service may be implemented as a single server or have an internal structure involving multiple servers and proxies. There may be complex pa ...
. Usually in order to get presence information a watcher have to subscribe for it to a presence server. When subscribed, the watcher receives event notifications as presence information changes. Alternatively watcher may fetch presence information without subscribing to it.
References
*Day, M., J. Rosenberg, and H. Sugano. "A Model for Presence and Instant Messaging." RFC 2778. February 2000.
Instant messaging
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