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Re: [ontolog-forum] The class of the planet Venus

To: ontolog-forum@xxxxxxxxxxxxxxxx
From: John F Sowa <sowa@xxxxxxxxxxx>
Date: Fri, 13 Jul 2012 09:06:33 -0400
Message-id: <50001D59.7080403@xxxxxxxxxxx>
Ed, Chris, Pat, and Leo,    (01)

> I think I was misled by John's terminology "model of the world".
> I fully agree that the semantic model for a logic language is a set
> of things in the "world of interest".
> And if what John meant by a "model of the world" is a collection of
> things and states taken to be a domain of discourse, then I withdraw
> my complaint.    (02)

I intended to use the word 'model' in that broader sense.    (03)

> there are two very different notions of "model" in the general KR
> community (in which I include the ontology community), one coming out
> of mathematical logic and the other coming out of engineering...    (04)

> And the latter sense is much more widely understood than the former,
> by about three or four orders of magnitude. Which is why I avoided
> using the word entirely when writing the RDF semantics specs, and
> used the circumlocution "satisfying interpretation" for the logical
> sense of "model".    (05)

I agree with both of those comments.  But I'd like to mention an article
by Carl Adam Petri (of Petri-net fame), who emphasized the commonality:    (06)

Petri, Carl Adam (1977) Modelling as a communication discipline,
in H. Beilner & E. Gelenbe, eds., _Meaning, Modelling, and
Evaluating Computer Systems_, Amsterdam: North-Holland, 435-449.    (07)

He observed that when you say X is a model for Y, that means X has
some structural similarity Z to an important aspect of Y.    (08)

If you consider all three components -- X, Y, Z -- an engineering model
and a Tarski-style model have a fundamental similarity:    (09)

  1. Each one has a text in some language that states the important
     aspect Z:  engineering spec's or axioms of some theory.    (010)

  2. Each one follows the text Z to construct a model X using
     appropriate resources:  an engineering model constructed from
     physical material or a mathematical model constructed from sets.
     But with modern computers, the engineering models are also
     mathematical.  They just use a wider range of mathematics.    (011)

  3. The purpose of the model is to simulate or describe an intended
     subject Y, which may be something that exists in the physical
     world or it may be some hypothetical or future construction.    (012)

> ... something that was shown to be very important during
> Ontology Summit 2012, which is the distinction between
> specification/design/model and eventual artifact.    (013)

Yes.  In Tarski-style model theory, the applications to the
world (present or future) are often ignored.  But engineers
are strongly focused on the applications.    (014)

> See above. We don't have to use the term [model] at all.    (015)

I agree.  But I would also point out that an engineering model
can be considered an interpretation of the specifications.    (016)

And in the interests of full disclosure, I must admit that
I have an ulterior motive:  I have also been using the word
'model' for the "mental models" that the cognitive scientists
and neuroscientists have been talking about.    (017)

That same triad of text Z, mental model X, and subject Y
arises in cog. sci.  But that's another issue to be avoided
when talking to people who have a day job they're working on.    (018)

John    (019)

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