Re: [wsbpel] Issue - R13 - BPEL partner link assignments

b) is definitely a correct approach:
1. REQ assigns from "callback partner link" (myRole) to a variable
2. REQ passes the EPR to R
3. R forwards the EPR to B
4. B assigns the EPR to "callback partner link" (partnerRole)
5. B invokes callback provided by REQ
6. REQ receives the response

The variables for the partner link assignments are typed with
sref:service-ref. The contents are opaque for R and B, that is,
whatever the EPR looks like, REQ is both producer and consumer
of this EPR.