Programming Jabber

Name

query — Required

Synopsis

<iq type='get' to='yak'>
<query xmlns='jabber:iq:version'/>
</iq>

We’ve already seen the <query/> subelement performing the task of container for the info/query activity.

• For an IQ-get, the subelement usually just contains a qualifying namespace that in turn defines the essence of the get activity. This is evident in the example here, where the <iq/> element is a retrieval of the server (yak) version information.

• For an IQ-set, it contains the qualifying namespace and also child tags that hold the data to be set, as in this example, in which a vCard (an electronic “business card”) is being updated:

  SEND: <iq type='set'>
          <vCard xmlns='vcard-temp' version='3.0'>
          ... [vCard information] ...
          </vCard>
        </iq>

• When result information is returned, it is enclosed within a <query/> subelement qualified with the appropriate namespace, as in this IQ-result response to the earlier request for server version information:

  RECV: <iq type='result' to='dj@yak/Work' from='yak'>
          <query xmlns='jabber:iq:version'>
            <name>jsm</name>
            <version>1.4.1</version>
            <os>Linux 2.2.12-45SAP</os>
          </query>
        </iq>

  Of course, there are some results that don’t carry any further information—the so-called Boolean results. When there’s no information to return in a result, the <query/> subelement isn’t necessary. A typical case in which a Boolean result is returned is on successfully authenticating to the Jabber server (where the credentials are sent in an IQ-set request in the jabber:iq:auth ...