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>
    <alllinks galcontinue="Boundary" />
  </query-continue>
  <query>
    <pages>
      <page ns="0" title="Barycenter" missing="" />
      <page ns="0" title="Basic" missing="" />
      <page ns="0" title="Basic definition" missing="" />
      <page ns="0" title="Boole" missing="" />
      <page ns="0" title="Boolean algebra" missing="" />
      <page ns="0" title="Boolean functions" missing="" />
      <page ns="0" title="Boolean variable" missing="" />
      <page pageid="323" ns="0" title="Boolean-valued function" />
      <page pageid="321" ns="0" title="Boolean domain" />
      <page pageid="322" ns="0" title="Boolean function" />
    </pages>
  </query>
</api>