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RE: MEP proposal

From: Assaf Arkin <arkin@intalio.com>
Date: Fri, 21 Feb 2003 13:03:55 -0800
To: "Jacek Kopecky" <jacek@systinet.com>, "Amelia A. Lewis" <alewis@tibco.com>
Cc: "Martin Gudgin" <mgudgin@microsoft.com>, "Jeffrey Schlimmer" <jeffsch@windows.microsoft.com>, "WS Description WG" <www-ws-desc@w3.org>

> -----Original Message-----
> From: www-ws-desc-request@w3.org [mailto:www-ws-desc-request@w3.org]On
> Behalf Of Jacek Kopecky
> Sent: Friday, February 21, 2003 10:34 AM
> To: Amelia A. Lewis
> Cc: Martin Gudgin; Jeffrey Schlimmer; WS Description WG
> Subject: Re: MEP proposal
> While interface does alude to RPC, I used the term as I believe it was
> initially conceived - the point where things connect. I don't know what
> else to use to describe the contract between exactly two roles (as
> interfaces do), so I guess I'll keep using it.

This is also how the term is used in WSCI to define an contract that may be
arbitrarily complex.

> The term 'operation' is applicable in all three: a system has
> operations, an interaction would be an operation, and interfaces also
> have operations.

This is absolutely true. The term operation has two distinct meaning, it can
be as complex as any interaction, or it can be as simple as 'given inputs
product output' (the mathematical term). The mathematical and computing use
of the word points towards the simpler use case (e.g. addition,
substraction, instruction).

> I think visible intermediaries should be describable with WSDL. A
> visible intermediary is a service, too, so you can't dismiss this again
> saying we decided WSDL is from the point of view of the service. 8-)
> But a visible intermediary does have the other side that logically
> belongs in the same operation but contains a third role.

This is treading into choreography.

If I want to interact with service A which in order to perform the operation
must interact with service B, at the operation level I only care about
service A. I need to send it a message and receive a response, everything
else is beyond the atomic nature of an operation.

On the other hand, in a bigger picture I would like to know that my
interaction with A leads to an interaction with B, perhaps because I will be
interacting with B directly later on. The bigger picture can be arbitrary
complex, either we leave it out of the scope of MEPs, or we extend MEPs to
the point where we have a choreography language.

I don't see why we would want to do it in both places.

Received on Friday, 21 February 2003 16:05:12 UTC

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