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Re: Abstract messages [Was: Multi-Party Binding Scenario]

From: Jon Dart <jdart@tibco.com>
Date: Wed, 02 Apr 2003 09:44:10 -0800
Message-ID: <3E8B216A.8080106@tibco.com>
To: "Fletcher Tony" <Tony.Fletcher@choreology.com>
CC: public-ws-chor@w3.org

Fletcher, Tony wrote:

> So my personal inclination at present (not a considered company
> position!) is to say:
> 
> 1.   Yes
> 
> 2.   Yes
> 
> 3.   No (not for the Choreography itself, but have a binding to WSDL and
> XML message schema)
> 

I think 1. Yes + 2. Yes really implies No to issue 3 (dependence on 
WSDL), because if you have both an reference to an actual message 
definition (not the definition itself) in the choreography, and if you 
have decision points also coded by reference, then you are independent 
of message format.

Note that neither WSCI nor BPEL has seen fit to do things quite this way.

Also IMO if you do this, it is not clear how you effect the actual 
binding. BPEL abstracts the message definition out of the choreography, 
but part of BPEL is also the serviceLinkType, which binds a role to a 
WSDL portType. What you're proposing, I think, is that we also be able 
to bind to an ASN.1 format message. But lacking a WSDL description for 
it, how do you do that? Furthermore, how would you describe parts of the 
message? Opaqueness in the choreography flow itself is fine, but at some 
point you need to make message definition and message components 
non-opaque, otherwise you don't really have a choreography defined in 
enough detail that a client can interoperate with it. Which was why the 
alternative of describing the message in WSDL, and assuming it had an 
XML representation (whatever its "native form may be) was attactive.

--Jon
Received on Wednesday, 2 April 2003 12:44:17 UTC

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