RE: Perdurantist planning problems (was: RE: RE: SUO: Re: Ballot Comment)
Pat,
I agree with your point below - which is important - "the planner isn't
reasoning *about* knowledge, but reasoning
*with* knowledge (about the world, even if incomplete.)". In my language
this is saying that from one perspective epistemology is dependent upon
ontology. Hence ontology (the world) is important.
Regards,
Chris
-----Original Message-----
From: pat hayes [SMTP:phayes@ai.uwf.edu]
Sent: Monday, September 10, 2001 7:07 PM
To: Chris Partridge
Cc: standard-upper-ontology@ieee.org
Subject: RE: Perdurantist planning problems (was: RE: RE: SUO: Re: Ballot
Comment)
>Pat,
>
>With regard to the first point below, I did not make myself clear.
>
>It seems to me that many of the branchings one looks at in planning are
>reflections of one's ignorance about the world, rather then possible
>futures of the actual world - though we believe them to be possible
futures
>(not the same thing).
OK, point take, and I agree. However, I may not agree with what may
be your next conclusion, if that were going to be that the proper way
to actually do planning would be to reason about states of knowledge
explicitly (since planning is a basically epistemic matter....) I'd
say that world-planning is about the world even if it is what might
be called meta-epistemic. The knowledge that the planner has about
the world is incomplete, and that observation is an epistemic one;
but the planner isn't reasoning *about* knowledge, but reasoning
*with* knowledge (about the world, even if incomplete.)
Pat
>A contrived example: I make an agreement with you at 2pm that I can use
>your car to go home tonight if I need to (you trust me enough) - but I
must
>tell you by 4pm. I then work out the options - one being that I use your
>car. However, unbeknownst to me and you, your car was destroyed at 1pm.
The
>option that I am considering is not a possible (ontological) future of the
>actual world I am in - though it is epistemically possible for both you
and
>me.
>
>It seems to me that it is easy to fudge the difference between branching
>(ontological) futures and epistemic ones - and that planning is based upon
>what we know rather than the way the world actually is in all its detail.
>
>I seem to recall an article on the web by David Chalmers on epistemic
space
>where he also talks about this distinction.
>
>Regards,
>Chris
>
>
>-----Original Message-----
>From: pat hayes [SMTP:phayes@ai.uwf.edu]
>Sent: Tuesday, September 04, 2001 10:17 PM
>To: Chris Partridge
>Cc: standard-upper-ontology@ieee.org
>Subject: RE: Perdurantist planning problems (was: RE: RE: SUO:
>Re: Ballot
>Comment)
>
>
> >Pat,
> >
> >This seems to me to illustrate the difference between a (philosophical)
> >ontology and an epistemology. That the branching (that Pat describes
>below)
> >is a function of epistemology (what is known) rather than time.
>
>That is one claim, but it's by no means obvious. Whether the actual
>physical universe is deterministic has been debated for a very long
>time and is in fact still a matter of debate. I gather the current
>best consensus among physicists is that it is in fact not
>deterministic, and that quantum collapse in effect is a kind of
>movement of the actual universe along a path in a tree of
>possibilities.
>
> >The reason
> >it seems to deal with time is that it presupposes the rule that we
cannot
> >know the future - but there are also some aspects of the past of which
we
> >are ignorant.
>
>Indeed, and that is a weakness of the situation calculus for general
>situated thinking about actions (eg one might well want to know what
>sequence of past events could have produced an observed property of
>the world, as in 'who moved my cheese?') It is still very useful,
>however.
>
>Pat
>
>
> >It seems to me (I make no claim to originality) that epistemology and
> >intertwined - that epistemology presupposes ontology and epistemology
>needs
> >to explain how we get to know ontology etc. etc.
> >
> >As Pat points out an agent's view of the world - rooted at a particular
> >place and time - with a certain store of knowledge, is very different
from
> >the community type perspective of an ontology such as the SUO. This
seems
> >to be ignored in simplistic definitions of an ontology as a conception -
> >but become clearly more of a problem when you start considering an
> >extensive ontology such as the SUO. Of course, branching is not the only
> >difference.
> >
> >Regards,
> >Chris
> >
> >-----Original Message-----
> >From: pat hayes [SMTP:phayes@ai.uwf.edu]
> >Sent: Saturday, September 01, 2001 12:18 AM
> >To: standard-upper-ontology@ieee.org
> >Cc: Matthew.R.West@is.shell.com; apease@ks.teknowledge.com
> >Subject: Perdurantist planning problems (was: RE: RE: SUO: Re: Ballot
> >Comment)
> >
> >
> >
> >Now that Adam and Matthew seem to be converging on a mutual
> >acceptance of a spatiotemporal ontology which descibes change in
> >terms of atemporal assertions about temporal parts, and since there
> >seems to be no chorus of protest from the endurantists at this
> >flagrant disregard for their philosophical scruples (Chris Menzel?
> >Mike Gruninger? Are you there?), allow me to mention one severely
> >practical problem with this approach.
> >
> >There is a well-entrenched tradition of 'action planning' in AI which
> >thinks of a dynamic world as moving through states under the control
> >of 'actions', and does planning by proving that states exist which
> >satisfy certain properties, extracting the sequence of actions to
> >achieve the goal by examining the proof. The oldest form of this is
> >planning in the situation calculus, but basically the same idea has
> >been used in a number of different settings. What all these have in
> >common is an assumption that it makes sense to reason about changes
> >in terms of a tree (or directed graph) of states and
> >state-transitions, where the states in the immediate 'future' of a
> >state are the alternative possibilities for the next state. Notice
> >that this picture combines two rather different modal ideas, in that
> >one 'dimension' (following paths in the graph) corresponds to time,
> >while the other (the fanouts from each node) to possibility. This is
> >very difficult to reconcile with the perdurantist (4-d) ontological
> >language, since there is no single spatiotemporal 'envelope' which
> >contains all the various possible futures of a given state.
> >
> >The situation is not impossible, since one can think of the planning
> >process as searching through a space of 'expanding' alternative
> >space-time bubbles, but it gets woefully complex to describe, in
> >painful contrast to the elegant style of function nesting which
> >arises from the older ontological frameworks; and this inelegance has
> >some drastic and possibly fatal computational consequences, since one
> >cannot rely on unification to automatically keep track of the
> >spatiotemporal-part relationships which arise here in the same way
> >that it automatically creates action-sequence terms; the 'fit' of the
> >tree of possible futures with the tree-structure of action terms is a
> >very valuable byproduct of logical reasoning; for many people, in
> >fact, the main product.
> >
> >BTW, this is why I long ago gave up on what was otherwise the very
> >promising 4-d approach to naive physics which I developed in my old
> >'liquids' paper. If what one wants to do is simply describe a
> >particular timeline, then perdurantism has many advantages. But to
> >reason about a complex system of partially overlapping possibilities,
> >it seems to give rise to many ugly and intractable problems, and the
> >elegance of the endurantist simplicity of the situation calculus and
> >its variations becomes very appealing by contrast.
> >
> >Pat Hayes.
> >---------------------------------------------------------------------
> >(650)859 6569 w
> >(650)494 3973 h (until September)
> >phayes@ai.uwf.edu
> >http://www.coginst.uwf.edu/~phayes
>
>---------------------------------------------------------------------
>(650)859 6569 w
>(650)494 3973 h (until September)
>phayes@ai.uwf.edu
>http://www.coginst.uwf.edu/~phayes
---------------------------------------------------------------------
(650)859 6569 w
(650)494 3973 h (until September)
phayes@ai.uwf.edu
http://www.coginst.uwf.edu/~phayes