[wsrp] [interfaces] session creation

It's still unclear to me why the consumer would need request the 
creation of a session to the producer, maybe I've missed something 
during the last conf call. I would like to know what scenarios can not 
be covered using a mechanism similar to the HTTP Cookies protocol:

1) A client makes a request to a consumer
2) The consumer creates a Csession for the client
3) The consumer makes a request to a producer
4) The producer creates a Psession for the consumer request
5) The producer, together with the response, sends back the PsessionID 
to the consumer
6) The consumer stores the PsessionID in the Csession
7) The consumer, together with the response, sends back the CsessionID 
to the client
8) Future client requests to the consumer contain the CsessionID
9) Future consumer requests to the producer contain the PsessionID 
associated to the CsessionID of the incoming client request
10) Sessions end/expire re-triggering the session acquisition steps on 
subsequent requests

In the absence of a consumer-producer session, the concurrency problem 
-when producer receives concurrent consumer requests for different 
portlets, where all the requests are to fulfill the same client request- 
can be easily solved by having the consumer sending a transient common 
ID with all the consumer-producer requests for the same client request. 
This transient common ID would help the producer to manage the case when 
portlets serving requests for the same client request ask for a session 
to be created. Note that this transient common ID for consumer-producer 
requests does not have to be same for different client-consumer 
requests, although the protocol could use the same placeholder for the 
transient common ID and for the consumer-producer session ID 
(PsessionID). From the producer perspective, a transient common ID or a 
consumer-producer session ID are no different except for the fact that 
the later has been created by the producer, it could be used to store 
transient local data associated with the session and it could have a 
expiration.

Regards.

Alejandro