SOAP-Gateway output message

at the moment I am trying to run the SOAP-Gateway. But there is a problem with the output message of the gateway.

What I am trying to do is calling an Web Service (in fact it is a BPEL-Process exposed as web service). This web service returns an output (an double) which I want to use in the sequence. The gateway runs quite well until the output message is produced. SOAP returns the following failure:

… com.softwareag.xbridge.exceptions.ProcessMessageException: com.softwareag.xbridge.exceptions.XException: No on_error sequence found. Exception: “org.activebpel.rt.bpel.AeBusinessProcessException: Error building output message” in sequence…

I have no idea how I can expose the output of the web service to a propertie or an XML-file of the sequence document.

What I have done is setting a skeletonResponse.xml, which contains only

<return> </return>

. I than want to write the output message to this XML-file.

What do I have to type in the XPath expression of the OUT-Property during processing the SOAP-Gateway-Assistant?

Thanks in advance for help