WS-Addressing is a transport-neutral mechanism by which web services communicate addressing information. SOAP envelopes & headers used within web services for transporting data throught transport layers like HTTP does not possess intelligence to specify unique addressing information. Hence, WS-Addressing evolved which contained endpoint references (EPR) and message information headers for identification. This information is processed independently of the transport mechanism or application.
For reference on WS-Addressing click here
By default, Oracle BPEL PM implements WS-Addressing for all asynchronous web service calls, hence we don't have to explicitly implement identification relationship between the incoming & outgoing messages.
Hope this will help