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Re: BurdettML comments (MEPs)

From: Jon Dart <jdart@tibco.com>
Date: Fri, 27 Jun 2003 09:09:40 -0700
Message-ID: <3EFC6C44.6080002@tibco.com>
To: "Burdett David" <david.burdett@commerceone.com>
CC: "'public-ws-chor@w3.org '" <public-ws-chor@w3.org>

See below.

Burdett, David wrote:
> Jon
> 
> See comments in line below.
> 
> David
> 
> -----Original Message-----
> From: Jon Dart [mailto:jdart@tibco.com]
> Sent: Wednesday, June 25, 2003 9:56 AM
> To: Burdett David
> Cc: 'public-ws-chor@w3.org '
> Subject: Re: BurdettML comments
> 
> 
> Burdett, David wrote:
> 
> 
>>Also in my spec I assumed that an Interaction was implmented by a single
>>message (ignoring signals) sent from one role to another. In your example
>>for "DoLogin" to succeed, you would need two messages the LoginRequest
> 
> from
> 
>>the client to the server and the LoginResponse from the server to the
>>client. The result could be either succeed or fail.
> 
> 
> One issue here for me is how this maps into the SOAP/WSDL layer (if 
> there is one). The simple way to implement login is with a request/reply 
> MEP. Then there are two messages, as you suggest, but it is one 
> operation, in the WSDL sense of the term. Maybe it should be possible to 
> include such a MEP in the choreography without explicitly showing the 
> two messages - it is a logical unit.
> <DB>I like this idea in principle, however some MEPs consist of a
> request/response whilst others consist of a single message. I can't easily
> think of how you could easily combine these different types of MEPs into a
> single choreography definition.</DB>

I am not sure how best to handle this, either.

A MEP is really a mini-choregraphy, with its own state machine (see e.g. 
http://www.w3.org/TR/soap12-part2/#soapsupmep).

IMO what you want is the ability to represent a step in the choreography 
as an instance of a MEP (or possibly some other, more complex 
sub-choreography). An example of this kind of nesting is in my 
discussion of the travel agency user scenario.

The general pattern should be reusable, although the actual schema of 
the message inputs and outputs vary.

There is a relevant recent discussion of MEPs in WSA: 
http://lists.w3.org/Archives/Public/www-ws-arch/2003Jun/0223.html

--Jon
Received on Friday, 27 June 2003 12:09:54 GMT

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