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Partial executability/ determinism of a Chor description language

From: Fletcher, Tony <Tony.Fletcher@choreology.com>
Date: Thu, 22 May 2003 10:40:52 +0100
Message-ID: <221369570DEDF346AE42821041345E89194D66@exchange1.corp.choreology.com>
To: <public-ws-chor@w3.org>
Dear Colleagues,
 
I would like to clarify in my own mind and continue a discussion o the
degree to which a Choreography description language (CDL) is
deterministic or 'executable'.  I think this issue links to previous
threads on the use of information from messages, or not.
 
I think we all agree that a CDL will only give a very partial
description of the behaviour of any 'entity' playing a particular role
(and that you do need a full programming language such as Java or C#
for any sort of 'complete' description.
 
However, consider the following:
 
Role A sends message 1 to role B
 
Role B replies with message 2 to role A
 
At this point there may now be say three different messages that A could
next send to B according to the CDL instance and given no other
information.
 
Now suppose that message 1 was an order message and message 2 an order
response with a critical information field that says 'accept' or
'reject'.
 
The CDL could now say that role A can examine the incoming message 2
extract the semantic accept or reject and if reject then send message 3
else send message 4 or message 5 (means of determining which is not
shown in this CDL instance, but would be in the CPL for that role).
 
Without being dependent on the precise syntax of messages, only some of
the semantic elements, I think that some people in this group would like
the above behaviour to be supported by the WS-Chor language and thus
support for this behaviour to be a requirement.
 
Others seem to be arguing for no dependence on message content at all -
perhaps just the name of the message received(?).  Can we reach an
amicable consensus?
 
Best Regards     Tony
A M Fletcher
 
Cohesions 1.0 (TM)
 
Business transaction management software for application coordination
 
Choreology Ltd., 13 Austin Friars, London EC2N 2JX     UK
Tel: +44 (0) 20 76701787   Fax: +44 (0) 20 7670 1785  Mobile: +44 (0)
7801 948219
tony.fletcher@choreology.com     (Home: amfletcher@iee.org)
 
Received on Thursday, 22 May 2003 05:41:06 GMT

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