- From: Drew McDermott <drew.mcdermott@yale.edu>
- Date: Mon, 28 Jun 2004 14:19:54 -0400 (EDT)
- To: public-sws-ig@w3.org
> > [Jeff Dalton]
> > I'm not sure that's enough to make it an effect as such,
> > rather than some kind of post-condition, because presumably
> > the way it's made true that ?n1 is < 5 is by giving ?n1
> > some specific value that is less than 5, and it's giving it
> > that value that's the effect, strictly speaking.
> [Donal Murtagh]
> Whether it's an effect or post-condition, do you know of planners that=20
> allow such conditional expressions in the postconditions/effects of=
> operators?
I don't see how Donal's question follows up to Jeff's remark.
The answer to the question, ignoring Jeff's remark, is: Pretty much
all planners allows conditional expressions in effects. They
correspond to the 'when' clause in PDDL:
(:action A
:precondition P0
:effect (and ...
(when P1 E)))
P0 must be true for A to be feasible at all. P1 must be true for A to
have the effect E. P1 is called a _secondary precondition_.
> > [Jeff]
> > One problem for a planner is that if it wants, say, ?n1 to be
> > less than 10, one way to get that is to use something that makes
> > ?n1 less than 5, and that requires a reasoner that could make
> > such connections.
> [Donal]
> I'm guessing "and most planners aren't capable of such reasoning" is=
> implied?
Your guess is correct.
-- Drew
--
-- Drew McDermott
Yale Computer Science Department
Received on Monday, 28 June 2004 14:20:02 UTC