How compile expression in Copy

[Michele]

Hello, I have a problem. I'm developing a BPEL parser and I need to manage
copies inside an assign Activity.
I don't know how extract the variabibles (ex. Search) from an expression
like :

<![CDATA[concat("Stai cercando: ",$Search.SearchPart/what, "
",$Search.SearchPart/where)]]>

from the following snippet:

   <bpel:copy>
                <bpel:from>
                    <![CDATA[concat("Stai cercando:
",$Search.SearchPart/what, " ",$Search.SearchPart/where)]]>
                </bpel:from>
                <bpel:to part="UpdatePart" variable="Update">
                    <bpel:query
queryLanguage="urn:oasis:names:tc:wsbpel:2.0:sublang:xpath1.0"><![CDATA[resultXML]]></bpel:query>
                </bpel:to>
            </bpel:copy>

I know I have to compile the expression and obtain a "OProcess"., but I
don't know how to do that.
thank