You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <alltransclusions gatcontinue="Prettytable|29" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Open Science Repository at the Information and Communication Services Group at the University of Rostock" />
      <page pageid="5" ns="0" title="OLQM" />
      <page pageid="10" ns="0" title="Geographical distribution of nodes" />
      <page pageid="14" ns="0" title="OLSR" />
      <page pageid="19" ns="0" title="OLQ" />
      <page pageid="25" ns="0" title="OLQ one week" />
      <page pageid="26" ns="0" title="ThmONAG" />
      <page pageid="27" ns="0" title="OLQ one hour" />
    </pages>
  </query>
</api>