From: David Martin ([email protected])
Date: 02/11/05
Greetings Mike and all joint committee folks -
Lest you guys get bored, a bunch of us are grappling with the question 
of how to use a SWRL expression as the value of a property instance, and 
I'd very much appreciate your views on this.
For example, in OWL-S an AtomicProcess has a precondition, which we want
to express in SWRL.  Here's a simplistic example of the kind of thing we
might like to do:
<AtomicProcess>
   <hasPrecondition>
     <ruleml:Imp>
       <ruleml:body>
         <!-- empty body -->
       </ruleml:body>
       <ruleml:head>
        <swrl:IndividualPropertyAtom>
          <swrl:propertyPredicate
            rdf:resource="⪚hasCreditCardOfType"/>
          <swrl:argument1 rdf:resource="#user" />
          <swrl:argument2 rdf:resource="#VISA" />
        </swrl:IndividualPropertyAtom>
       </ruleml:head>
     </ruleml:Imp>
   </hasPrecondition>
   ....
</AtomicProcess>
This says that the precondition for the atomic process is that the user 
must have a VISA card (user is a variable that will get bound to some 
kind of user ID, when the process runs).
So here are my questions:
(1) Is this legal to use an Imp instance in this way, as the value of a 
property instance?
(1a) In general, can SWRL classes like Imp and IndividualPropertyAtom be 
instantiated and used in all the same ways that ordinary OWL classes can 
be used in OWL-DL?  (Is it even right to think of these as OWL classes?)
(2) If the above example is legit, how about if we omit the Imp and body 
and head elements, and just nest the IndividualPropertyAtom directly 
inside the hasPrecondition tag?
(3) If the answer to (1) or (2) is "no" - is it any different for SWRL-FOL?
(4) If the above example is legit, and *if* we forget about RDF 
semantics, will a SWRL reasoner treat the Imp as if it were a non-nested 
assertion, and try to reason with it?  Or will it simply record that 
there's an Imp instance related to an AtomicProcess instance?
Thanks!
- David Martin
(on behalf of various people working on OWL-S and Protege-based OWL editors)
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