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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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The following terminology is used with presence services:<br />

Principal Human, program, or a collection of humans,<br />

programs, or both, that chooses to appear to the<br />

presence service as a single actor, distinct from all<br />

other principals.<br />

Presentity A presence entity is called a presentity. Each<br />

presentity provides presence information to a<br />

presence service. The presentity is not (usually)<br />

located within the presence service; the presence<br />

service only has a recent version of the presentity's<br />

presence information. The presentity initiates<br />

changes in the presence information, which is then<br />

distributed by the presence service.<br />

Presence information Consists of one or more presence tuples.<br />

Presence tuple Consists of elements associated with a presentity’s<br />

presence information. for example, status <strong>and</strong><br />

communication address.<br />

Status A distinguished part of the presence information of a<br />

presentity. Status has at least the mutually-exclusive<br />

values open <strong>and</strong> closed, which have meaning for the<br />

presentity being online or offline.<br />

Open A distinguished value of the status marker. The<br />

associated presentity is online. Contrast with closed.<br />

Closed A distinguished value of the status marker. The<br />

associated presentity is offline. Contrast with open.<br />

Communication address Consists of communication means <strong>and</strong> a contact<br />

address.<br />

Communication means Indicates a method whereby communication can<br />

take place. An instant message service is one<br />

example of a communication means.<br />

Contact address A specific point of contact through some<br />

communication means.<br />

Other presence markup Any additional information included in the presence<br />

information of a presentity.<br />

Fetcher A form of watcher that has asked the presence<br />

service for the presence information of one or more<br />

presentities.<br />

Poller A fetcher that requests presence information on a<br />

regular basis.<br />

708 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong>

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