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Re: Web Services Choreography Description Language (WS-CDL) proposal

From: Steve Ross-Talbot <steve@enigmatec.net>
Date: Mon, 13 Oct 2003 14:42:28 +0100
Cc: public-ws-chor@w3.org
To: Nickolas Kavantzas <nickolas.kavantzas@oracle.com>
Message-Id: <15F6711C-FD83-11D7-8EF1-000393D13C9A@enigmatec.net>

Nick,

here are the comments that I have already sent to you wrt to Oracle  
contribution.

I now share them as a matter of record.

My main issue with the spec is that it involves active participation in  
the choreography between participants, which means that legacy  
webservices are not going to be able to be included, which will limit  
the take up.

It also does not 'extend' or build upon existing web service  
interactions (i.e. message exchanges). Instead it defines the concept  
of shared state between participants, which needs to be synchronized  
before associated interactions can be triggered. This is very ECA like,  
as opposed to passive monitoring of workflow.

I don't think state information should be visible outside the web  
service, other than the information provided as part of a message  
exchange. My preferred choreography notation would simply define a  
workflow coordination of high level message types, which reference the  
actual message types in the WSDL interfaces. Also, I think it would be  
better to approach the problem by defining a collection of short lived  
stateful choreographies, that when they are each performed, obtain the  
relevant business context as part of their initial interactions (e.g.  
first request should provide a reference/customer id, etc. - which is  
the same model as most human and electronic interactions in today's  
business/web). This can also be mapped on to the more short lived  
connection oriented approach.

I think the language should be in support of a passive approach, acting  
as a definition of an agreed collaboration, which can then be used to  
(1) help construct the individual (decoupled) participant web services,  
based on the observable behaviour they must exhibit, and then (2) used  
by each participant to verify that they (and their partners) are  
correctly implementing the choreography.

A central mechanism for policing the choreography is not required if  
each participant (that is interested in obeying the choreography  
definition) has the necessary checks defined in their local  
implementations - which can be aided by the use of tools that  
understand the external observable behaviour that is required.

Cheers

Steve T

On Thursday, September 11, 2003, at 12:08  am, Nickolas Kavantzas wrote:

>
> Oracle would like to submit a document for consideration by the W3C  
> Choreography Working Group.
>
> This is being provided under the normal W3C IPR rules.
>
> The document can be found at:
> http://lists.w3.org/Archives/Public/www-archive/2003Sep/att-0018/ 
> wscdl_v1.zip
>
> We would like to request time on next's week F2F agenda for presenting  
> an overview of this submission.
>
> --
> Regards,
>
> Nick and Jeff
>
>
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Received on Monday, 13 October 2003 09:42:32 GMT

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