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Re: section 2.2.22 Message Exchange Pattern (MEP)

From: David Booth <dbooth@w3.org>
Date: Mon, 14 Jul 2003 19:27:35 -0400
Message-Id: <>
To: jones@research.att.com
Cc: www-ws-arch@w3.org, chrisfer@us.ibm.com

At 10:41 AM 7/11/2003 -0400, jones@research.att.com wrote:
>Well, I guess I see this as a terminological issue.

Yes, I agree.

>I certainly agree
>that there will be more complex "messaging patterns" than (SOAP) MEPs,
>but for me the SOAP notion of an "exchange" has always had in view the
>set of communicating participants involved in a message and its

I never made the assumption, and I don't see it suggested in the SOAP 
definition of MEP[2]:

         "A Message Exchange Pattern (MEP) is a template that establishes
         a pattern for the exchange of messages between SOAP nodes."

Personally, I think all we need to do is drop the word "SOAP" and change 
the word "nodes" to "agent", in order to be more consistent with the rest 
of our text:

         "A Message Exchange Pattern (MEP) is a template that establishes
         a pattern for the exchange of messages between nodes."

 From a WS Architecture point of view, I think that definition nails it.

>For example, a messaging pattern that involved A and B
>exchanging messages, followed by A and C exchanging messages (as
>dictated by some application logic) is certainly a messaging pattern.
>I just wouldn't call it a message *exchange* pattern in the SOAP/WSDL

Well, I may not call it a "SOAP MEP" or a "WSDL MEP", because SOAP and WSDL 
have named specific MEPs that they recognize, but I would call it an MEP 
just as much as a one-way message pattern is an MEP.

>. . . At the very least, if we widen the MEP term to include arbitrary
>messaging patterns (MPs), it would still be good to have a term that
>corresponds to the earlier notion of an MEP that involves "a message
>and its responses".

I find that notion both vague and unnecessary.  I think we would be better 
served by being more specific: Use the term "WSDL MEP" to refer to WSDL 
MEPs, and "SOAP MEP" to refer to SOAP MEPs.  Those terms have clear, 
well-defined meanings and don't require any new definitions.  If you want a 
term that refers to the union of the two, just use "SOAP or WSDL MEPs".

>This will be the natural unit upon which
>higher-level messaging patterns are constructed.

Any language for defining higher order patterns would have to be specific 
about which patterns are the basic building blocks, such as: "Higher order 
patterns are built out of WSDL MEPs."

David Booth
W3C Fellow / Hewlett-Packard
Telephone: +1.617.253.1273
Received on Monday, 14 July 2003 19:28:18 UTC

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