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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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19.2 Presence Information Data Format (PIDF)<br />

RFC 3859 – Common Profile for Presence (CPP) defines common semantics<br />

<strong>and</strong> data formats for presence to facilitate the creation of gateways between<br />

presence services. This assists with the interoperability issues between<br />

presence services. RFC 3863 defines the Presence Information Data Format<br />

(PIDF) as a common presence data format for CPP-compliant presence<br />

protocols, allowing presence information to be transferred across CPP-compliant<br />

protocol boundaries without modification. This is because the PIDF encodes<br />

presence information in Extensible Markup Language (XML). The presence<br />

information is therefore hierarchically structured <strong>and</strong> fully extensible.<br />

The PIDF is as follows:<br />

► Presentity URL: This is the “pres” Uniform Resource Locator (URL) of the<br />

presentity.<br />

► List of presence tuples, which contain the following elements:<br />

– Identifier: Token to identify this tuple within the presence information.<br />

– Status: Open/Closed or extension status values, or both.<br />

– Communication address: Communication means <strong>and</strong> contact address of<br />

this tuple (optional). A contact address can be an e-mail address or a<br />

telephone number. RFC 3953 discusses the Telephone Number Mapping<br />

(ENUM) service for presence.<br />

– Relative priority: Numerical value specifying the priority of this<br />

communication address (optional).<br />

– Time stamp: Time stamp of the change of this tuple (optional).<br />

– Human-readable comment: Free text memo about this tuple (optional).<br />

– Presentity human-readable comment: Free text memo about the<br />

presentity (optional).<br />

– Timed-status: Status of a presentity that is either no longer valid or covers<br />

some future time period. (This element is an addition to the PIDF <strong>and</strong> is<br />

discussed in RFC 4481.)<br />

For further information regarding these elements, refer to RFC 3863 <strong>and</strong> RFC<br />

4481 for the timed-status element specifically.<br />

Rich Presence Information Data (RPID) format is discussed in RFC 4480, which<br />

includes other XML elements that extend the PIDF. These elements include:<br />

► activities: Enumerates what the person is doing.<br />

► class: An identifier that groups similar person elements, devices, or services.<br />

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

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