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RE: Definition of Choreography

From: Ugo Corda <UCorda@SeeBeyond.com>
Date: Tue, 22 Oct 2002 10:33:20 -0700
Message-ID: <C513FB68F8200244B570543EF3FC65370A855BD7@MAIL1.stc.com>
To: "'Assaf Arkin'" <arkin@intalio.com>
Cc: www-ws-arch@w3.org

It looks like you are assuming that the Request/Response MEP is only
synchronous, which is not the case. (In particular, in a sequence of two
such interactions between X and Y, the second response can get back to X
before the first response).

Ugo

-----Original Message-----
From: Assaf Arkin [mailto:arkin@intalio.com]
Sent: Tuesday, October 22, 2002 10:25 AM
To: Ugo Corda
Cc: www-ws-arch@w3.org
Subject: RE: Definition of Choreography


Just my $0.2c

You have service X and service Y. Service Y defines a request-response
operation. Service X sends the input message to service Y and receives the
output message. That entails, as far as I understand it, that service Y
receives the input message and produces the output message. Once service X
has received the output message, service Y has completed the operation
(strictly concerning what WSDL defines of it).

Given a sequence of two such interactions, once service X has received the
second response message, it knows that service Y has performed both
operations.

From the interaction, service X can infer what service Y is doing at a
particular point in time. That is a synchronous operation.

You have service X and service Y. Service Y defines a one-way operation.
Service X sends the input message to service Y over high latency protocol.
Service X does not wait for a response message, it goes on to do the next
thing. Later on, service Y receives the input message and completes the
operation (again, strictly concerning what WSDL defines of it).

Given a sequence of two such interactions, once service X has sent the
second message, it has no guarantee that service Y has performed the
operation twice, or even once.

From this interaction, service X cannot infer what service Y is doing at a
particular point in time, and assuming the message is never lost, it can
only tell what Y will do at a future point in time. That is asynchronous.

arkin



Arkin,

>WSDL defines an abstract message as a container of multiple message parts.
>That message can be used in multiple operations. The operation definition
>gives it the proper semantics and also indicates the direction of the
>message flow, and whether it completes synchronously or asynchronously.

I don't see where WSDL says anything about the fact that an operation is
synchronous or asynchronous. Could you please clarify?

Thank you,
Ugo
Received on Tuesday, 22 October 2002 13:33:52 GMT

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