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RE: Definition of Choreography

From: Burdett, David <david.burdett@commerceone.com>
Date: Fri, 18 Oct 2002 14:04:33 -0700
Message-ID: <C1E0143CD365A445A4417083BF6F42CC053D13CE@C1plenaexm07.commerceone.com>
To: "'Mark Baker'" <distobj@acm.org>, "Burdett, David" <david.burdett@commerceone.com>
Cc: "'Cutler, Roger (RogerCutler)'" <RogerCutler@ChevronTexaco.com>, "'Dave Hollander'" <dmh@contivo.com>, "Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>, www-ws-arch@w3.org


I actually think that both the interface AND the choreography need to be

The interface needs to be standardized so that, for example, there is only
one widely recognized way of doing something common, for example getting an
exchange rate.

Here there is a distinction between: the definition of the service
interface, and the implementation of that service interface definition.

Suppose there were 20 banks that all provided a free service to existing
customers where they allowed their customers to query on individual exchange

From an implementation perspective it would be much easier if all the banks
used the same SOAP messages, with the same actions used in the same sequence
etc as then if one implementation wasn't working you could switch to another
very easily.

WSDL, however is generally used to just define an individual service
implementation which means that each implementation could be different. I
don't think that WSDL currently makes this distinction clear.

Choreographies need to be standardized for reasons of re-use (see my earlier
email) and because you can get the same interface used in multiple
choreographies, for example the exchange rate service described earlier
could be used:
1. As part of a query when someone is looking up exchange rates on a web
2. As part of order-pre-pricing process before sending the order to the
3. To calculate the values on an invoice which the seller wants to send back
to the buyer

Each of these could use the same service or different services with the same
service interface, but they would have different choreographies.


-----Original Message-----
From: Mark Baker [mailto:distobj@acm.org]
Sent: Friday, October 18, 2002 1:10 PM
To: Burdett, David
Cc: 'Cutler, Roger (RogerCutler)'; 'Dave Hollander'; 'Mark Baker';
Champion, Mike; www-ws-arch@w3.org
Subject: Re: Definition of Choreography

On Fri, Oct 18, 2002 at 12:40:00PM -0700, Burdett, David wrote:
> However what is much more useful, I would almost say essential, is
> standardized definitions of actual choreographies, i.e. how you place an
> order, how to submit an invoice, etc.

I agree, but all that needs to be standardized is the "interface" to
these processes.  Whether they trigger a complex choreographed operation
lasting weeks or months, or just complete the order then and there, the
interface can be the same.  After that, it's just a game of "follow the
declared state transitions" (which has its own issues, but they're

Mark Baker, CTO, Idokorro Mobile.  Ottawa, Ontario, CANADA.
http://www.markbaker.ca             http://www.idokorro.com
Received on Friday, 18 October 2002 17:04:28 UTC

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