Assign error with complex type return message

Question

Dear all,
I have an axis web service with complex type return message. When I invoke the web service, and try to assign one element of the result to other variable, it fails with following error message(BPEL Fault:{http://schemas.xmlsoap.org/ws/2003/03/business-process/}selectionFailure{}
The invoking web service and assignment BPEL source is as follows:
<invoke name="registerConference" partnerLink="conferenceCenter" portType="tns:ConfArrangementPort" operation="Conference_Register" inputVariable="registerInput" outputVariable="registerOutput"/>
<copy>
<from variable="registerOutput" part="Conference_RegisterReturn" query="/Conference_RegisterReturn/confcity"></from>
<to variable="bookHotelInput" part="si" query="/si/city"/>
</copy>
I tunneled the response SOAP message:
==== Response ====
HTTP/1.1 200 OK
Content-Type: text/xml; charset=utf-8
Date: Sun, 31 Oct 2004 08:28:27 GMT
Server: Apache Coyote/1.0
Connection: close
<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<ns1:Conference_RegisterResponse soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" xmlns:ns1="http://conference.sjtu.edu">
<ns1:Conference_RegisterReturn href="#id0"/>
</ns1:Conference_RegisterResponse>
<multiRef id="id0" soapenc:root="0" soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" xsi:type="ns2:ConfInfo" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:ns2="http://conference.sjtu.edu">
<confcity xsi:type="xsd:string">star</confcity>
<confend xsi:type="xsd:string">20041120</confend>
<confstart xsi:type="xsd:string">20041116</confstart>
</multiRef>
</soapenv:Body>
</soapenv:Envelope>
==============
However, when i check the invoke activity audit trail, it return the following info:
<messages>
<registerInput>
<part xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance" name="gi">
<gi xmlns="http://conference.sjtu.edu">
<attendeename xmlns="">ss</attendeename>
<confname xmlns="">hh</confname>
</gi>
</part>
</registerInput>
<registerOutput>
<part xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance" name="Conference_RegisterReturn">
<ns1:Conference_RegisterReturn xmlns:ns1="http://conference.sjtu.edu" href="#id0" />
</part>
</registerOutput>
</messages>
The detailed value of the return message lost, only leaving the href. Can I find the desired value again? should I try another XPATH expression? should I parse the result from the SOAP message directly? Or it's a problem of the system itself?
Hope you can do me a favor, thanks.

Answer 1

From Axis's user guide: RPC services default to the soap section 5 encoding rules, objects will be encoded via "multi-ref" serialization. Document services do not use any encoding (so in particular, you won't see multiref object serialization or SOAP-style arrays on the wire)
May be I should try document service style instead of RPC. Thanks for your reply.