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Re: Definition of Choreography

From: Paul Prescod <paul@prescod.net>
Date: Sat, 19 Oct 2002 15:56:39 -0700
Message-ID: <3DB1E327.80407@prescod.net>
To: "Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>
CC: www-ws-arch@w3.org

Champion, Mike wrote:
> 
>...
> 
> Hmm ... in the absurdly hypothetical situation where I come into a
> restaurant and let my Bluetooth or WiFi-enabled PDA deal with an automated
> waiter via SOAP messages, I would disagree.  I might want water and salad,
> then a a main course with wine, and then dessert with coffee.  I for one
> would be highly annoyed if dinner started with dessert and wine, then I got
> salad and coffee, and ended with a main course and water.

Let's not get too obsessed with the restaurant example. The point is 
that if it is a precondition of the desert that you've already had a 
meal then it would be very simple to express that by simply giving you a 
"had-a-meal" token which you present when you ask for desert. If you got 
one from your best friend who had a meal yesterday, then (from a 
business sense) that's fine, no matter what the social custom is.

If there is a business problem that cannot be solved _conveinently_ in 
this way, then we can easily end the conversation with a single a use case.

 > ...
> Tim has a point, and to pick up another of Tim's mantras, I think we should
> be focussed on doing the "minimum required to declare victory" here. 

Business rules as preconditions and postconditions of operations is the 
MRTDV. And it is a *subset* of what you need to do in order to do 
choreogaphy. Choreography is preconditions + postconditions + temporal 
constraints on how you achieve them. All I'm saying is that we can throw 
away the last factor. In the rare case where it is really necessary 
(haven't heard a use case) it can be easily expressed in terms of the 
first two.

  Paul Prescod
Received on Saturday, 19 October 2002 18:57:18 GMT

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