Re: [OWL-S] Negative effects/delete lists

Drew,

I agree that the problem is hard, and that we need some notion
of a local-closed world assumption to make any headway.  The
problem is also complicated by the "ramification problem" --
that processes can also have indirect effects as the result of
state constraints that exist in an ontology.

A hasty example is the following:

Let's say I have a constraint that says

  teach(sheila,Date) -> location(sheila,toronto,Date)
  (i.e, to teach my class on Date, I must be located in Toronto on Date)

but let's say that I execute a web service to book a flight from Toronto
to San Francisco on 04-01-04.

The direct effect is that location(sheila,san_francisco,04-01-04), but the
indirect effect is
  not teach(sheila,04-01-04)

What's even harder than putting a local-closed world assumption on
the direct effects is integrating the ramifications appropriate.

*example disclaimer:  OK...when you book a flight, the actual effect is
that your *expected* location will be the destination of the flight.
That's true with any web service that talks about effects that will occur
in the future.  The principle behind the example still holds

- Sheila McIlraith
  University of Toronto


On Thu, 1 Apr 2004, Drew McDermott wrote:

>
>
> > > [Sheila McIlraith]
> > >
> > > I wonder if we can write a tool to ensure that negative effects coding
> > > rules are not violated?
> >
> > [Bijan Parsia]
> > I believe so.
>  ...
> > Is it anything more than checking for each effect literal whether its
> > negation is entailed by the KB?
> >
> There's a long history of work on this problem, which is really the
> problem of figuring out how to find a coherent story about what
> Strips-style action definitions actually _mean_.  It is easy to come
> up with axiom sets for which deleting (or, for that matter, adding) an
> assertion produces semantic fruit salad very quickly.  It's amazing
> how little all this seems to matter in practice.
>
> I think the real question hiding in the bushes here is what kinds of
> closed-world assumptions we can make in the semantic-web-service biz.
> Reiter's book explains how to handle both closed and open initial
> conditions within a clean logic framework, but in practice I tend to
> assume that you need a lot of closedness assumptions for inference to
> be tractable.
>
>                                              -- Drew
>
> --
>                                    -- Drew McDermott
>                                       Yale Computer Science Department
>
>

Received on Thursday, 1 April 2004 22:38:05 UTC