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Intra- of Inter-service composition

From: Marta Sabou <marta@cs.vu.nl>
Date: Fri, 21 Feb 2003 16:17:55 +0100
Message-ID: <3E564323.D96A16A2@cs.vu.nl>
To: www-ws@w3.org



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?

Cheers,
-- 
 Marta Sabou
Received on Friday, 21 February 2003 10:20:34 GMT

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