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RE: Hypermedia workflow

From: Assaf Arkin <arkin@intalio.com>
Date: Fri, 20 Dec 2002 20:24:54 -0800
To: "Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>, <www-ws-arch@w3.org>

Representing myself as a co-author of the WSCI specification I would like to
clarify that it was a design goal that a choreography definition would
*describe* the interaction and would not be required in order to perform the

Whether or not a choreography is described using a choreography language
(and in my understanding that applies equally well to BPEL4WS), whether or
not you have that choreography, lost it or decided to ignore it, you would
still use the Web service in exactly the same way.

What the choreography buys you is the ability to understand how it will
behave without having to try it so you can tailor an application that
participates in the choreography. It's just another way of describing how
two systems would work once they actually start exchanging message and is no
longer relevant when you get to conduct the exchange. But it helps you in
building these systems.

Think of choreography as a cooking recipe. You don't need it in order to
cook, you need ingredients. You would whisk eggs the same way whether you
have a recipe or inventing your own dish. But having a recipe allows you to
exchange it with others so they can all cook the same dish, open up a
restuarant that serves consistent food, and publish recipe books.

The value of a choreography language is that it allows a development tool to
give you a lot of services based on that understanding, simplifying the
overall development effort. This is where it adds value over existing
solutions like UML diagrams, PDF documents and doodles on napkins.


> > Sure, nothing's preventing the rules from being shared.  It's just
> > optional.  Perhaps there's some legal reason to share it, I don't
> > know.
> >
> > Anyhow, it's not needed in order to *execute* the process, which seems
> > to me to be the important thing.
> OK, I see your point and have no problem with it.  I personally think that
> main point of a web service choreography is to *describe* it, and the
> execution is an "implementation detail" for the purposes of this WG.
> Nevertheless, I agree that the execution could be done RESTfully and
> [putting on my Software AG hat] it is a very good idea to build
> choreographed services using a scalable/reliable XML repository
> with an HTTP
> interface :-)
Received on Friday, 20 December 2002 23:25:43 UTC

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