<wsdl:interface name="Order"
      sawsdl:modelReference="http://example.org/categorization/products/electronics">
  <wsdl:operation name="order" pattern="http://www.w3.org/ns/wsdl/in-out"
      sawsdl:modelReference="http://www.w3.org/2002/ws/sawsdl/spec/ontology/purchaseorder#RequestPurchaseOrder">
    <wsdl:input element="OrderRequest" />
    <wsdl:output element="OrderResponse" />
  </wsdl:operation>
</wsdl:interface>