BPEL partner link assignments

["Andi Abes" <aabes@sonicsoftware.com>]

I'm trying to understand the semantics of assignment to and from partner
links in BPEL, and the spec left me with a few open questions.

For the purpose of discussion, I'm considering a simple "router" process
(R). 
The one operation exposed by this process includes 2 parts:
 1) an amount (xsd:int)
 2) the EPR of the requesting process (process REQ)

This operation is one way.

Based on content in the incoming request, the router chooses a process
(process B) to "forward" the request to. Process B is expected to invoke
an agreed upon operation on Process REQ, using the EPR information in
the message.

There are 2 possible implementations:
a) 
  The router process assigns from the receiving partner link to a
variable (or message part) which is then relayed to process B. Process B
then performs its activities and assigns this value to the a partner
link which it uses to invoke an operation on REQ.

b) 
  REQ is responsible to assign from "myrole" on the partner link facing
the router into the a message it eventually sends it.


Based on my reading of the 8/23 draft, both implementations are
supported.


The questions for which I have no clear answer are:

1) 
Is implementation option A supported ?
Assuming it is, the spec in silent on IMA activities affecting the
partner link for the purpose of assign activities, and the lifetime of
the partner link value.

My expectation would be that once an IMA activity has completed,
assigning from the partner link would yield the reply-to EPR. 

Would this also require the partner link variants of the Assign activity
to include a messageExchange attribute.

2)
Assuming the above is valid, what would the schema type of the variable(
or message part) into which the EPR is assigned be?
 serf:service-reference  - in the case of message part, this would cause
BPEL specific types to be "leaked" into the abstract WSDL.
 wsa:endpoint-reference - this would bind the BPEL process to a specific
addressing scheme.

In either case, it would be useful for the spec to be specific about
this point (and an example would be great).

3)

Section 6.3 ("Endpoint References")states:
The <sref:service-ref> element is not always exposed to WS-BPEL process
definitions. For example, it is not exposed in an assignment from the
endpoint reference of myRole of partnerLink-A to that of partnerRole of
partnerLink-B. On the contrary, it is exposed in an 
wsbpel-specification-assignment from a messageType or element based
variable through expression or from a literal <sref:service-ref>.

Section 8.4.3 states that the following is not a valid assignment:
the selection result of the from-spec is a variable of a WSDL message
type and that of the to-spec is not, or vice versa (parts of variables,
selections of variable parts, or endpoint references cannot be assigned
to/from variables of WSDL message types directly).


It is not clear if these to sections are contradicting.
If assignments to/from partner links is allowed (which is explicitly
stated in section 8.4), what are the valid combinations? 



Thanks in advance for your considerations and clarifications.