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Re: question: relation between WS-CDL and WSCI

From: Titi Roman <dumitru.roman@deri.ie>
Date: Tue, 13 Apr 2004 04:03:36 +0300
Message-ID: <000901c420f3$27621e60$906c9ad5@titi>
To: "Steve Ross-Talbot" <steve@enigmatec.net>
Cc: "WS-Choreography List" <public-ws-chor@w3.org>

Hi Steve,
Thanks a lot for you answers. Still some questions/comments in-line...

----- Original Message -----
From: Steve Ross-Talbot <steve@enigmatec.net>
To: Titi Roman <dumitru.roman@deri.ie>
Cc: WS-Choreography List <public-ws-chor@w3.org>
Sent: Sunday, April 11, 2004 11:46 PM
Subject: Re: question: relation between WS-CDL and WSCI


>
> Fair question Titi.
>
> Okay where do I start....
> First of all WSCI was an executable language.

I am a little bit confused here...In the WSCI 1.0
(http://www.w3.org/TR/wsci/) in section 1.6.2 it says that WSCI "is
declarative and cannot, by itself, be executed." (I also haven't heared
about amy execution environments for WSCI). I understood that WSCI possess
an operational semantics, did you refer to this when you said that WSCI was
an executable language?

> Secondly WSCI has no formal basis at all.

I have recently read a paper (A. Brogi, C. Canal, E. Pimentel, A.
Vallecillo: "Formalizing Web Services Choreographies.",  First International
Workshop on Web Services and Formal Methods (WS-FM 2004), Pisa February
23-24, 2004.) in which the authors propose a logical formalism based on
process algebra as a formal basis for WSCI (mainly for reasoning about the
compatibility of the WSCI descriptions of 2 or more web services).

> One thing did cross the boundary into, namely the concept of the
> "global model". This remains a principle focus of the approach we have
> taken.

Does this mean that WS-CDL supports only "global model"(i.e. the
multi-participant view of the overall message exchange)? What about the view
of the overall message exchange as seen from one participant? Isn't WS-CDL
supposed to support also this view?

> We tightened up by basing things around some formalism (the
> pi-calculus). We recruited some academic experts in the field (Robin
> Milner, Nobuku Yoshida and Kohei Honda) to help make this real. And we
> issued WS-CDL (editors draft and overview document).

I think I miss some basic things here:
Why do you need a formalism in the choreography context (where can be seen
the usefulness of using such a fomalism for a choreography language)? Where
is it actually needed?
Which is the reason for choosing pi-calculus and not other formalism (e.g.
Abstract States Machines)?
Where can be seen the usefulness of using pi-calculus as an underlying
fromalizm for WS-CDL?


Thanks a lot!
Regards,
Titi Roman
Received on Sunday, 11 April 2004 20:58:12 UTC

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