External Schema

• Put a schema attribute on the model element.

  <model xmlns="http://www.w3.org/2002/xforms" id="p1"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
    schema="doughnuts.xsd" >
    <instance>
      <doughnuts xmlns="http://www.example.org/doughnuts/">
        <quantity/>
      </doughnuts>
    </instance>
    <submission action="http://www.example.org/formprocessor.php"
        method="post" id="q0" />
  </model>

• Useful for more complex constraints: derived types, complex types, etc.