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Re: question: relation between WS-CDL and WSCI

From: Assaf Arkin <arkin@intalio.com>
Date: Tue, 13 Apr 2004 13:14:45 -0700
Message-ID: <407C4A35.9070201@intalio.com>
To: Titi Roman <dumitru.roman@deri.ie>
Cc: Steve Ross-Talbot <steve@enigmatec.net>, WS-Choreography List <public-ws-chor@w3.org>
Titi Roman wrote:

>>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?
WSCI was definitely not intended to be executable, but describe the 
observable message exchange between the participants. It did focus on a 
level of abstraction that some other proposals would consider 
"operational", but any language can be viewed as operational compared to 
a more abstract 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).
The model for describing the behavior of any one participant/process and 
the composition of that behavior into larger processes is based on 
mobile process calculus.

>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?
Formalism allows you to make a lot of proofs about the language itself, 
but more interesting, about the specifications you produce using that 
language. In the case of WSCI, formalism becomes more important as a way 
to derive conclusions about compositions, and it allows you to leverage 
the extensive work done in the field of process calculus.


>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!
>Titi Roman

"Those who can, do; those who can't, make screenshots"

Assaf Arkin                                          arkin@intalio.com
Intalio Inc.                                           www.intalio.com
The Business Process Management Company                 (650) 577 4700

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Received on Tuesday, 13 April 2004 16:15:12 UTC

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