For instant messaging, a presence information watcher is an entity that requests presence information about a presentity from a presence service. 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.