k.com CSeq: 2 NOTIFY Max-Forwards: 70 Event: presence Subscription- - State: active; expires=3400 Contact: sip:server.handbook.com Content-Type: application/pidf+xml Content-Length: [New PIDF Document] M6: The watcher confirms receipt of the NOTIFY request. SIP/2.0 200 OK Via: SIP/2.0/UDP server.handbook.com;branch=z9hG4bk4cd42a; received=168.0.2.6 To: sip:subscribe@handbook.com>;tag=12341234 From: <sip:notify@handbook.com>;tag=abcd1234 Call-ID: 10275342@handbook.com CSeq: 2 NOTIFY Content-Length: 0 5.4 Presence Information Data Format (PIDF) 5.4.1 Overview Presence Information Data Format (PIDF), as a common presence data for- mat for presence protocols, allows presence information to be transferred © 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security across these protocols [5]. In the notify mechanism, the PIDF is stored in the body of the notify message, such as M3 and M5 in previous message flow Figures. The PIDF encodes presence information in eXtensible Markup Lan- guage (XML). PRESENCE INFORMATION consists of an arbitrary number of elements called PRESENCE TUPLES. 5.4.2 Presence Information Contents 5.4.2.1 Content PRESENTITY URL: specifies the "pres" URL of the PRESENTITY. List of PRESENCE TUPLES PRESENTITY human readable comment: free text memo about the PRE-SENTITY (optional). 5.4.2.2 XML-Encoded PIDF <presence> <tuple> <status> <basic> <contact> <priority> <note> <timestamp> <tuple> C 2009 by Taylor & Francis Group, LLC SIP Event Notification and Presence Information <tuple> A PIDF object is a well-formed XML document containing an encoding declaration in the XML declaration, e.g., "<?xml version='1.0' encoding 'UTF-8'?>." The <presence> element: The root of an "application/pidf+xml" object is a <presence> element associated with the presence information namespace. This contains any number of <tuple> elements. The <presence> element MUST have an 'entity' attribute. The value of the 'entity' attribute is the URL of the PRESENTITY. The <presence> element contains a nam