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From: Drew McDermott <drew.mcdermott@yale.edu>
Date: Sun, 12 Dec 2004 03:51:17 +0000 (GMT)
To: public-sws-ig@w3.org
Message-ID: <E1CdM6y-0003G9-OF@frink.w3.org>

> [Tatiana Vieira]
>    I need help! I have a process definition in OWL-S that is something like:
> 
>  CompositeProcess A composedOf
>     Sequence
>        CompositeProcess B composedOf
>            AtomicProcess C
>            AtomicProcess D
>        AtomicProcess E
>        
>    AtomicProcess D produces as output a list (subClassOf
>    &objList;List) of classes X.  So, the output of process B is the
>    output of process C plus this list. However, the AtomicProcess E
>    receives as input the output of process C and just one class
>    X. This process must be invoked as many times as are the instances
>    of class X in the list produced as process D output. How can I
>    represent this in OWL-S 1.1? Can anyone give me a help?

You need a loop, and loops exist only in embryonic form in Owl-S.

The main reason for this is that it's been hard enough getting the
abstractions right without bringing in loops.  Another reason is that
as soon as you add loops you've got Turing completeness (presumably),
and reasoning about processes becomes much more complex.  If we want
to automate reasoning, then it seems to be a plausible tactic to
focus on processes for which we have reasoning algorithms that might
actually work.

However, we're obviously going to need some kind of looping
processes.  This mailing list is as good a forum as any for discussing
what they should look like.  My own opinion is that it would be better
to have a lot of special-purpose loops that come up in the WS domain
rather than a few general-purpose control structures.  The example you
raise is a good starting point.  A 'forall' construct that performed a
process for each element of a list would work for you (correct?); what
are some other good candidate control structures?

-- 

                                         -- Drew McDermott
                                            Yale University
                                            Computer Science Department

All languages have the same syntax as Lisp, but most insist on
encrypting it (by the use of grammar).
Received on Sunday, 12 December 2004 05:17:36 GMT

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