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Re: [ontac-forum] Theories, Models, Reasoning, Language, and Truth

To: Chris Menzel <cmenzel@xxxxxxxx>, ONTAC-WG General Discussion <ontac-forum@xxxxxxxxxxxxxx>
Cc: "Lichtblau, Dale" <Del@xxxxxxx>
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Fri, 16 Dec 2005 23:25:20 -0500
Message-id: <43A39330.70804@xxxxxxxxxxx>
Chris and Dale,    (01)

Thanks, Chris, for the plug and for writing the
response.  I had been tending to other things,
and I overlooked that message.    (02)

Just two points:    (03)

  1. The word _model_ is one of those heavily overused
     words in English that has many, many different
     definitions in various fields of science and
     engineering.  Chris stated the common usage in
     logic, which follows Tarski.  For a nontechnical
     summary by Tarski himself, see his 1944 paper:    (04)

     http://www.jfsowa.com/logic/tarski.htm    (05)

  2. Ontology is a particularly confusing place to use
     the word _model_ because it brings together so many
     different fields that confusion is inevitable.
     Following is a brief excerpt from my 1984 book,
     in which I cited a point made by C. A. Petri
     (of Petri-net fame, as opposed to Julius of
     Petri-dish fame).    (06)

________________________________________________________    (07)

The word _model_ has multiple meanings in engineering, logic,
and common speech.  Petri (1977) noted three different meanings
in the phrases _model of an airplane_, _model of an axiom system_,
and _model farm_:    (08)

  - Simulation.  A model airplane is a simplified system that
    simulates some significant characteristics of some other
    system in the real world or a possible world.    (09)

  - Realization.  A model for a set of axioms is a data structure
    for which those axioms are true.  Consistent axioms may have
    many different models, but inconsistent axioms have no model.    (010)

  - Prototype.  A model farm is an ideal or standard for evaluating
    other less perfect farms or for designing new ones.    (011)

Petri maintained that a common basis should be found for these three
different ways of modeling.    (012)

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