High Quality Content by WIKIPEDIA articles! 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. In computer and telecommunications networks, presence information is a status indicator that conveys ability and willingness of a potential communication partner--for example a user--to communicate. A user's client provides presence information (presence state) via a network connection to a presence service, which is stored in what constitutes his personal availability record (called a presentity) and can be made available for distribution to other users (called watchers) to convey his availability for communication. Presence information has wide application in many communication services and is one of the innovations driving the popularity of instant messaging or recent implementations of voice over IP clients.

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