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Re: Intra- of Inter-service composition

From: Monika Solanki <monika@dmu.ac.uk>
Date: Fri, 21 Feb 2003 16:16:27 +0000
Message-ID: <3E5650DB.7000703@dmu.ac.uk>
To: Marta Sabou <marta@cs.vu.nl>, "'www-ws@w3.org'" <www-ws@w3.org>

I believe that DAML-S should be able to cater for the kind of scenario 
you have highlighted. The registry that publishes the profile, publishes 
the process model and the grounding details with it. I does not make 
sense to publish only the profile as all these models are dependent on 
each other. Depending on user inputs and constraints, the agent 
responsible for composing the service should be able to infer the 
composition model from the process and grounding details of the 
services, once it has discovered their service profiles for composition. 
I think that the agent would have to compose a runtime process model 
that includes the process models from all the services needed for the 
composition maybe based on some kind of an elementary
workflow model specified by the user. I agree that the example on the 
website is not representative of this kind of a scenario.


P.S. It would be interesting to have some more inputs on this issue from 
other members of the list.

Marta Sabou wrote:

>Hi all, 
>I've read though the postings of this mailing list but I could not find an answer to the issue bellow. Can you help me out?
>DAML-S papers claim that (among others) *dynamic* discovery and
>composition of services is supported by DAML-S. I have some
>questions about the composition in DAML-S.
>1) Does composition refer to "intra-service" composition? The
>examples on the DAML-S web site demonstrate how the process model
>(the internal composition of processes) of a service can be
>described. And indeed the DAML-S Process ontology restricts
>composition to entities of type Process (or ControlConstruct).
>2) Does composition mean also "inter-service" composition? Is it
>possible to specify a service as composed of multiple services?
>If yes, am I correct in saying that (judging from point 1): if a
>service (say S3) is composed of two other services (S1 and S2)
>then the process of S3 will have to refer to the processes of S1
>and S2? In my opinion this is the only way DAML-S allows to
>specify a service composed of other services. This is ok as long
>as we know which services should be composed. But what happens in
>cases when the exact services which should be composed are not
>known a-priori? What if we only know the profiles of services that
>should be composed and want to "dynamically" (at execution time)
>determine which service to call? Is DAML-S suited for these "non deterministic" scenarios?

Monika Solanki
De Montfort University
Software Technology Research Laboratory
Hawthorn building, H00.18
The Gateway.
Leicester LE1 9BH, UK

phone: +44 (0)116 250 6170 intern: 6170
email: monika@dmu.ac.uk <mailto:monika@dmu.ac.uk>
web: http://www.cse.dmu.ac.uk/~monika/ 
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Received on Friday, 21 February 2003 11:12:50 UTC

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