Each form has a model that shows the data to be submitted:
<model xmlns="http://www.w3.org/2002/xforms" id="p1"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema" >
   <instance>
    <doughnuts xmlns="http://www.example.org/doughnuts/">
      <quantity xsi:type="xsd:nonNegativeInteger"/>
    </doughnuts>
  </instance>
  <submission>
    We'll fill this in later...
  </submission>
</model>The single child element 
of the instance element is sent to the server.
The XML element sent to the server can have any well-formed structure and use any namespace.
In XHTML, this model is contained in  
 the head of the document.