W3C home > Mailing lists > Public > public-ws-chor@w3.org > June 2003

Re: choreography protocol

From: Sanjiva Weerawarana <sanjiva@watson.ibm.com>
Date: Mon, 23 Jun 2003 09:39:37 +0600
Message-ID: <02ad01c33939$13a78290$02c8a8c0@lankabook2>
To: <public-ws-chor@w3.org>

"Ugo Corda" <UCorda@SeeBeyond.com> writes:
> Yes, relying on the WSDL binding works when you can express that 
> binding in your spec. But what if you are writing a spec (e.g. a
> choreography spec) that prefers to leave WSDL bindings unspecified
> but still wants to talk about request/response on the same channel
> vs. on different channels? WSDL right now does not specify any way
> to express that. 

To me that's a programming model choice of the service invoker
and something that does not concern the service developer/describer:
they simply indicate the message pattern.

> It looks like BPEL got around this problem by saying that a 
> request/response on the same channel maps to a WSDL request/response
> MEP, while a request/response on different channels maps to two
> separate one-way MEPs (where the response one usually gets labeled
> "callback" as an additional syntactic sugar).

BPEL's solution does not assume that an <invoke> of a request-
response operation is such that both messages go on the same
channel. Its simply a blocking invocation .. waiting for a
response.

Yes, the use of one-way MEPs is the way to get async usage of
a request-response pattern in BPEL right now. However, IMO that's
not quite right .. I would've preferred to have a <send> primitive
which could be coupled with a <receive> to allow a BPEL author
to use request-response operations with an asynchronous model. 

Sanjiva.
Received on Sunday, 22 June 2003 23:39:33 GMT

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