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Re: DAML-S expressiveness challenge #1

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Thu, 21 Jun 2001 23:41:53 +0100 (BST)
Message-ID: <15154.30769.656308.260124@excalibur.cs.man.ac.uk>
To: David Martin <martin@AI.SRI.COM>
Cc: Tim Finin <finin@cs.umbc.edu>, "'Marcelo Tallis'" <mtallis@teknowledge.com>, "'Dan Connolly'" <connolly@w3.org>, www-rdf-logic@w3.org
On June 21, David Martin writes:
> 
> 
> Tim Finin wrote:
> 
> > > From: www-rdf-logic-request@w3.org
> > > [mailto:www-rdf-logic-request@w3.org] On Behalf Of Ian Horrocks
> > > ...
> > > Another possible interpretation is some sort of "role value
> > > map", as it is called in description logics. i.e., we may
> > > want to say that for all pairs of individuals (x,y) related
> > > by some property P (or some chain of properties), the P1
> > > property of x and the P2 property of y must have the same
> > > individual as their objects. I believe that we can't capture
> > > this in DAML+OIL - if we can then we made some mistake
> > > somewhere as the language would certainly be undecidable.
> >
> > I understood that this was what David needs, or something close to it.
> 
> Yes.
> 
> >
> > We want to be able to say, for example, that a Process has two
> > steps and that the output of step one must be the same individual
> > as the input of step two.  If we don't have this in our language then it
> > may be very hard to model complex processes which have sub-processes
> > that have constraints between them. For that matter, it will be hard to
> > model complex things composed of parts which have constraints among
> > them.
> 
> Well put.

As I said, in the general case this is known to be problematical.
However, what I should have added is that in the case where the
properties are UniqueProperties, which is often the case in practice,
then things are much easier. What you can usually say in this case is
that two different chains of UniqueProperties are (not) equal, e.g.,
that "output" and "nextProcess o input" (where "o" means composition
of properties) are equal (lead to the same object), with output,
nextProcess and input all being UniqueProperties.

Of course it would also be easy to express this using rules.

Ian
Received on Thursday, 21 June 2001 18:48:48 GMT

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