- From: Sheila McIlraith <sheila@cs.toronto.edu>
- Date: Wed, 28 Jan 2004 10:36:36 -0500
- To: Ian Horrocks <horrocks@cs.man.ac.uk>
- Cc: pat hayes <phayes@ihmc.us>, www-rdf-rules@w3.org, daml-process@bbn.com
Ian, An answer to your question below. On Tue, 27 Jan 2004, Ian Horrocks wrote: > On January 27, Sheila McIlraith writes: > > > > Ian, > > > > This is very helpful and interesting. <Though I need to work through > > an example in more details to understand all of the implications.> > > > > Regarding the question of whether the disjunctive literals in FOL would be > > encoded as classes or properties in OWL, my sense is that actions (e.g., > > a=pickup(x)) would be encoded as classes. I'll think about whether > > fluents in the situation calculus (predicates, indexed by the situation > > term, whose truth value can changes as a result of an action) could be > > encoded as classes as well. > > It isn't obvious to me how you can capture the relationship between a > and x using a class, but I will wait to hear more. Think of an action "a" (e.g., "pickup"), as being analogous to a process in the OWL-S service ontology, and the variable x, being analogous to an input parameter. In the original DAML-S, processes (e.g., "pickup") were modelled as classes, and their input (e.g., "x") as properties. In the most recent OWL-S, processes are now instances of classes, but the same relationship holds. > If it is the case > that you can encode one or other of the disjuncts as classes, then I > believe that you can capture the iff using the rewriting trick that I > described. Great. Sheila > > Ian > > > > > Sheila > > > > > > > > On Tue, 27 Jan 2004, Ian Horrocks wrote: > > > > > On January 25, Sheila McIlraith writes: > > > > > > > > > > > > Hi Pat, > > > > > > > > > > > > On Tue, 20 Jan 2004, pat hayes wrote: > > > > > > > > > > [...] > > > > > > > > holding(x, do(a,s)) IMPLIES ((a=pickup(x)) OR (holding(x,s) ) > > > > > > > > > > isn't, and isn't ever likely to be stateable in any rule language. > > > > > > But given that in SWRL combines rules with OWL, we get something much > > > more powerful which may allow us to state more that in normal rule > > > languages. E.g., if the disjunction in the head of the rule included a > > > unary predicate: > > > > > > Body IMPLIES P1(x) OR P2(x) > > > > > > then we would be able to state it in SWRL because we can rewrite it as > > > > > > Body AND NOT P2(x) IMPLIES P1(x) > > > > > > SWRL allows us to use (NOT P2) as a predicate (or we could use OWL to > > > assert that the class NOT-P2 as equivalent to the negation of the > > > class P2). > > > > > > Whether or not this kind of trick would work for the rule Pat wrote > > > would depend on how (a=pickup(x)) and (holding(x,s)) are encoded: if > > > they are encoded as binary predicates (OWL properties), then it seems > > > unlikely that we can express it in SWRL as it would amount to > > > providing property negation, and Uli Sattler has managed to convince > > > me that we (almost certainly) can't express property negation in SWRL. > > > > > > Regards, > > > > > > Ian > > > > -- > [To unsubscribe to this list send an email to "majdart@bbn.com" > with the following text in the BODY of the message "unsubscribe daml-process"] >
Received on Wednesday, 28 January 2004 10:37:14 UTC