Programming Jabber

Name

x — Optional

Synopsis

<presence from='dj@yak/Work' to='sabine@yak'>
  <status>Online</status>
  <priority>1</priority>
  <x xmlns='jabber:x:delay' from='dj@yak/Work'
     stamp='20011005T10:58:28'/>
</presence>

Just as with the <message/> element, extra information can be attached to the <presence/> element by means of the <x/> tag. In the same way, each <x/> tag must be qualified with a namespace.

While there aren’t many external uses for payloads in a <presence/> packet, the Jabber server uses this facility to add information. In this example, we see that dj@yak’s notification of availability (remember, type='available' is assumed for <presence/> packets without an explicit type attribute) is being sent to sabine@yak. While dj@yak connected to the Jabber server and sent his availability (which was stamped on receipt by the Jabber server) just before 11 a.m., sabine@yak is just logging on now (say, 30 minutes later). When she receives dj@yak’s presence, she knows how long that presence status has been valid for.

See Section 6.3 in Chapter 6 to find out what namespaces are available to qualify <x/>-included payloads.