W3C home > Mailing lists > Public > public-sws-ig@w3.org > June 2004

RE: OWL-S preconditions - practical issues

From: Dónal Murtagh <domurtag@cs.tcd.ie>
Date: Thu, 24 Jun 2004 16:33:48 +0100
Cc: <public-sws-ig@w3.org>
Message-ID: <000101c45a00$a5245ca0$163fe286@pc1568>

> > However, there doesn't appear to be any consensus about how 
> bindings 
> > should be specified.
> 
> There is, in broad detail. At least, we hashed it around a few times, 
> even on this list, I believe. There will be something. The basic 
> outlines are similar to PDDL. The exact syntax was still in the air 
> last I checked.

Any idea where I can find more details about this?

> 
> > For example, does the precondition above imply that
> > the AtomicProcess has an input #cc:
> >
> > <process:Input rdf:ID="cc">
> > 	<process:parameterType 
> > 
> rdf:resource="http://www.example.org/PaymentInstruments#CreditCard" />
> > 	<rdfs:label>Credit Card</rdfs:label>
> > </process:Input>
> >
> > Or is there another way to specify the binding of #cc to an 
> Input (or 
> > something else)?
> 
> It's the other way round. If there *is* such an input, it binds the 
> variable in the precondition. If not, it (IIRC) must have only one 
> possible binding and is bound against the world state.
>

er, what's IIRC?
 
> > Another matter which wasn't addressed during the recent 
> discussion is 
> > how a preconditon is tested/executed/evaluated - once the condition 
> > itself and its bindings have been correctly specified?
> 
> Well, it wasn't asked, either. Some of that will be application 
> dependent. It does depend on the specification of a KB (or 
> the like) to 
> evaluate the preconditions against (even after known bindings are 
> made).

If I recall correctly, you suggested that Pellet's conjunctive ABox
query answering module could be used to evaluate such preconditions. Is
this true, and if so, what syntax should they be expressed in if Pellet
were to be used for this purpose?

> 
> > Finally, for the purpose of service composition it is necessary to 
> > find processes which are compatible from the point of view of their 
> > preconditions and effects. For example, a process which has 
> an effect 
> > such as:
> [snip]
> > could never be executed immediately before a process which has a 
> > precondition such as that shown earlier, assuming #cc is 
> bound to the 
> > same instance in both cases. The point is that the compatibility of 
> > some preconditions and effects can be determined without binding 
> > information and it might be useful to distinguish these from 
> > preconditons and effects whose compatibility cannot be determined 
> > without binding information.
> 
> In what way? I mean, with some syntax? I would think you (the system) 
> could (would) just analyze it.

What I'd really like to know is whether there exists a tool which can
determine whether two conditional expressions are compatible.


Regards,
Dónal
Received on Thursday, 24 June 2004 11:34:00 UTC

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