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2 questions about perform, data-flow, and OWL-S 1.0

From: Jeff Dalton <jeff@inf.ed.ac.uk>
Date: Mon, 17 May 2004 17:16:26 +0100 (BST)
To: public-sws-ig@w3.org
Message-ID: <1084810586.40a8e55a7827f@mail.inf.ed.ac.uk>

For "perform", I'm starting with something Drew McDermott wrote:

  Some terminological points:  We now encourage the term  _process
  occurrence_ to mean the occurrence of a 'perform' for that process
  in another, complex process.  A process occurrence is not the same
  as the execution of a process, because of loops.

Suppose there's a text-translation service T that has process T#P,
and I want to translate a document that's in English to French and
back again, as a test of the translator.

I might try to use a process like this:

  (sequence (perform T#P) (perform T#P))

"Perform" helps make it clear that I and running the same process,
T#P, twice.  (More, of course, if someone puts my process in a loop.)

Question 1: How do I express such a process in OWL-S 1.0, where
there doesn't seem to be anything named "perform"?

Perhaps naively, I'd use something like this:

  <process:Sequence>
    <process:Process rdf:resource="T#P" />
    <process:Process rdf:resource="T#P" />
  </process:Sequence>

But does that have the right semantics?  I can't figure it out
from the OWL-S 1.0 Technical Overview or from Process.owl,
and I don't know of any more complete reference.

Question 2: How to I specify the data-flow?

Let's say that T#P has inputs T#inText and T#inLang,
outputs T#outText and T#outLang.

I want to say that an input in my composite process,
call it #originalText, goes into an occurrence of T#P.
If there was only one occurrence of T#P, I could say
#originalText at myProcess and T#inText at T#P had the
same value.

But there are two occurrences of T#P.  How do I say
which one I mean?  And how do I connect T#outText from
the first to the T#inText of the second?

Perhaps this calls for indirection.  Instead of having
a sequence that uses T#P directly, I could create two
new processes, P1 and P2.  They would each be, say,

  (Unordered T#P)

and they would have their own input and output parameters.

Then I could join up the data-flow at the top level using
those parameters, because they're all "at" different points.
#originalText would have the same-value as P1#inText at P1,
for example.  Or could I say T#inText at P1?

So I have
  P1 = (Unordered T#P)
  P2 = (Unordered T#P)
and may test process = (Sequence P1 P2).

But I'd still have the problem of saying, for instance,
that P1#intext at P1 and T#inText at T#P had the same value.
Since I still have two occurrences of T#P, how do I say which
one I mean?  It's looks like there's probably a scope rule,
so that if I attach the sameValues to P1, I'm referring to
the T#P in P, but I can't tell for sure from the Technical
Overview or Process.owl.

Also, this all seems excessively complicated, which makes me
unsure that this approach (using P1 and P2 etc) is the right
one.  Perhaps there's an RDF trick, or something, that I've
overlooked.

I'd appreciate any help anyone could give.

-- Jeff
Received on Monday, 17 May 2004 12:16:57 UTC

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