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Re: Planning under Description Logic ?--an obstacle towards WSAC

From: Drew McDermott <drew.mcdermott@yale.edu>
Date: Tue, 7 Dec 2004 21:06:19 +0000 (GMT)
To: public-sws-ig@w3.org
Message-ID: <E1CbmXt-000445-Dh@frink.w3.org>


> [Jeff (Dalton?) jeff@inf.ed.ac.uk] 

> However, HTN planners don't have to generate sequential plans.
> With O-Plan, for example, the final plan is still only a partial
> order.

For most partial-order planners, if the end result is not totally
ordered, that means that any total order consistent with the final
partial order will work.  So the semantics is still that of
interleaved atomic actions, not "true" concurrency.  I realize that
the "O" in "O-Plan" means "open," so O-Plan probably doesn't insist on
this interpretation (and probably doesn't support any particular
interpretation). 

However (I love caveats), once we move beyond purely classical
planning, and particular into domains with autonomous processes or
durative actions, the fact that atomic actions are interpreted as
non-concurrent becomes much less important.  That's because atomic
actions can start continuous changes in motion, and the semantics must
now say what happens over any interval in which two or more continuous
actions are all occurring.  Insisting that you can't turn on the
faucet and plug up the outlet at exactly the same time is unimportant
if exactly the same water level will be reached no matter which one
happened epsilon nanoseconds before the other.

For an example in the web-services domain, it's harmless to insist
that you can't order books from Amazon.com and BN.com at exactly the
same time, because the shipping processes launched will proceed over
intervals that might as well be identical.

                                             -- Drew


-- 

                                         -- Drew McDermott
                                            Yale University
                                            Computer Science Department
Received on Tuesday, 7 December 2004 21:06:53 GMT

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