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Re: [ontolog-forum] Confusion about 'model'

To: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Mon, 16 Jul 2007 11:29:13 -0500
Message-id: <6D34080F-BEC5-413C-AFFE-03BC833CEC88@xxxxxxx>

On Jul 15, 2007, at 6:51 AM, Smith, Barry wrote:    (01)

> Waclaw says
> You can use any language, of any expressivity, and still do silly
>> things.  Constrained expressivity does not mean that what you say  
>> about
>> the world is necessarily confused -- it is just a model which is much
>> more simple than the modeled reality.
> What, I wonder, does he mean by 'it'? Does he mean the language (is
> OWL or any other language intended to be a model of reality)? Or some
> statement or collection of statements in some language? When I say
> 'the cat is on the mat' I, for one, am not intending to create a
> model of reality. Rather, I am attempting to say something about
> reality itself (this very cat).
> BS
>    (02)

Yes, but part of the language problem we often get into about "model"  
is that a well-enough organized collection of things said about  
reality is often itself called a 'model' of that reality. So for  
example take almost any 3-d modeling software. If one tries to do a  
semantics of such a system, following the usual conventions for  
talking about semantics of software, one often finds that the  
internal "model" of the 3-d reality being modeled is something rather  
like a database, and that semanticists frequently (and with good  
reason) think of such a database as a collection of assertions. So  
the model of reality is a set of sentences asserted about that reality.    (03)

This gets especially awkward when we also talk about semantics using  
Tarskian terminology, where the 'model' of some sentences is a  
relational structure which is (one hopes) either itself an  
abstraction from an actual piece of reality, or perhaps structurally  
'similar to' the reality being model.., er, described. Putting this  
usage together with the one described above,  we have two senses of  
"model" being almost exact inversions of one another. The set of  
sentences is a "model" (sense 1) of a piece or aspect of reality just  
when that piece or aspect is a 'model' (Tarskian, sense 2) of the set  
of sentences. Sigh.    (04)

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