Xref: utzoo comp.ai:2240 sci.math:4517
Path: utzoo!attcan!uunet!husc6!mailrus!uflorida!fishwick
From: fishwick@uflorida.cis.ufl.EDU (Paul Fishwick)
Newsgroups: comp.ai,sci.math
Subject: state and change/continuous actions
Keywords: simulation, systems, commonsense knowledge
Message-ID: <18249@uflorida.cis.ufl.EDU>
Date: 16 Sep 88 21:25:29 GMT
Organization: UF CIS Department
Lines: 58


An inquiry into concepts of "state" and "change":

In browsing through Genesereth's and Nilsson's recent book "Logical 
Foundations of Artificial Intelligence," I find it interesting to
compare and contrast the concepts described in Chapter 11 - "State
and Change" with state/change concepts defined within systems
theory and simulation modeling. The authors make the following statement:
"Insufficient attention has been paid to the problem of continuous
actions." Now, a question that immediately comes to mind is "What problem?"
Perhaps, they are referring to the problem of defining semantics for
"how humans think about continuous actions." This leads to some
interesting questions:

 1) Clearly, the vast literature on math modeling is indicative of
    "how humans think about continuous actions." This knowledge is
    in a compiled form, and use of this knowledge has served
    science in an untold number of circumstances.

 2) If commonsense knowledge representation is the issue then we
    might want to ask a fundamental question "Why do we care about
    representing commonsense knowledge about continuous actions?"
    I can see 2 possible goals: One goal is to validate some given
    theory of commonsense "continuous action" knowledge against
    actual psychological data. Then we could say, for instance, that
    Theory XYZ reflects human thought and is therefore useful.
    I don't think it would be useful to increase our knowledge of
    mechanics or fluidics, for instance, but perhaps a psycho-therapist
    might find this knowledge useful. A second goal is to obtain
    a better model of the continuous action (this reflects the
    "AI is an approach to problem solving" method where one can
    study "how Johnny reasons when balls are bounced" and obtain
    a scientifically superior model regardless of its actual
    psychological validity). Has anyone seen a commonsense model
    of continuous action that is an improvement over systems of
    differential equations, graph based queueing models (and other
    assorted formal languages for systems and simulation)?

Obviously, I'm trying to spark some inter-group discussion and so I hope
that any responses will post to both the AI group (comp.ai) AND
the SIMULATION group (comp.simulation). In addition (sci.math) and
(comp.theory.dynamic-sys) may be appropriate.

I believe that Genesereth and Nilsson are quite correct that "reasoning
about time and continous actions" is an important issue. However, an
even more important issue revolves around people discussing 
concepts about "state," "time," and "change" by crossing disciplines.
Any thoughts?

-paul

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