Regarding the use of XQueryX in the WS-DAIX WSDL, there is the following element defined in the XQueryX schema to handle
 the trivial embedding of XQueryX:

<xsd:element name="xquery" type="xsd:string"/>

But, the XQuery port type WSDL defines the XQuery expression type as:

<xsd:complexType name="XQueryExpressionType">
   <xsd:complexContent>
      <xsd:extension base="wsdai:ExpressionType">
         <xsd:sequence>
            <xsd:element ref="xqx:module"/>
         </xsd:sequence>
       </xsd:extension>
   </xsd:complexContent>		
</xsd:complexType>

I think that this means that the trivial embedding can't be used. Perhaps <xsd:element ref="xqx:module"/> in the above 
should be changed to <xsd:any namespace="http://www.w3.org/2005/XQueryX"/>. This would allow XQuery expressions to be 
passed as strings, and would also be consistent with the way that XUpdate expressions are defined in the WSDL.
.