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

To: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>, Chris Menzel <chris.menzel@xxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Fri, 13 Jul 2012 00:42:34 -0500
Message-id: <F4683448-0502-4F43-B719-9ADE209B40C3@xxxxxxx>

On Jul 12, 2012, at 4:04 PM, Chris Menzel wrote:    (01)

> Right, on reflection I think the only issue here is that there are two very 
>different notions of "model" in the general KR community (in which I include 
>the ontology community), one coming out of mathematic logic and the other 
>coming out of engineering.    (02)

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".    (03)

> I think Ed was talking about the latter and I responded by talking about the 
>former  rather hastily, as I've in fact commented on this distinction before. 
>(Indeed, sets of axioms are sometimes called models as well, so there are 
>perhaps two distinct notions coming out of logic.) We can't (an arguably 
>shouldn't try) to prevent people in different communities from using the word 
>"model", but it would probably help to reduce confusion if those of us who are 
>in, or who talk to, people in both worlds should made a habit of qualifying 
>the word with, e.g., "engineering" (e.g., architectural designs), "logical" 
>(sets of axioms), and "semantic" (mathematical structures that interpret 
>formal languages). Or something.    (04)

See above. We don't have to use the term at all.     (05)

Pat    (06)

> 
> -chris
> 
> On Thu, Jul 12, 2012 at 3:54 PM, Obrst, Leo J. <lobrst@xxxxxxxxx> wrote:
> I think what Ed is getting at is something that was shown to be very 
>important during Ontology Summit 2012, which is the distinction between 
>specification/design/model and eventual artifact. In systems engineering (and 
>of course many other domains), one encounters these notions all the time. I 
>think a general theory of artifact (perhaps under a general theory of 
>description and realization) in an extensional ontology will typically be 
>sufficient (though hard).  However, that general theory of description and 
>realization may veer into or at least have to consider intensional aspects. 
>Matthew West and Henson Graves, among others, had an extensive discussion 
>about these notions for systems engineering in the Ontology Summit.
> 
>  
> Thanks,
> 
> Leo
> 
>  
> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx 
>[mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Chris Menzel
> Sent: Thursday, July 12, 2012 3:35 PM
> To: [ontolog-forum]
> Subject: Re: [ontolog-forum] The class of the planet Venus
> 
>  
> On Thu, Jul 12, 2012 at 11:03 AM, Ed Barkmeyer <edbark@xxxxxxxx> wrote:
> 
> John F Sowa wrote:
> >   4. The distinction between intensions and extensions can be used
> >      for individuals as well as for sets, relations, functions, and
> >      classes.  The basic point is that the extension is something
> >      in the world (or a model of the world), and the intension is
> >      a definition that is used to characterize and identify the
>  >     thing or things in the world (or some model of the world).
> 
> ...
> I do wish John had avoided the insertion of the parenthetical
> expressions in the above, because they weaken, perhaps to the point of
> confusing, his thesis.
> 
> The reason I object to John's parenthetical references to "models of the
> world" is that most "models" in this sense are intrinsically
> intensional. The artefacts in models are /constructed from/ the
> intensions, and two such artefacts may indeed be different even when the
> thing they are models of is the same.  A model of a building is not a
> building.  Two different models of the same building are different
> things, each conforming to a particular characterization of the
> building, whether the building itself exists or not, and in fact,
> whether or not the building in being actually possesses those
> characteristics.  (This is a critical idea in Herbert Simon's famous
> work "The Sciences of the Artificial", and in some of Ted Goranson's
> work.)  So it is in fact very difficult to argue that two
> conceptualizations of model elements are 'coextensive'.  The model
> element is a manifestation of the conceptualization, not the extension
> of it.  I would go so far as to say that a model element is a Frege
>  Zeichen -- a sign/symbol for the intension (Sinn).
> 
>  
> I'm afraid that, for the first time I can recall, I have to disagree with Ed 
>here. For there is absolutely no reason why the elements of a semantical model 
>of a logical language (including most any KR language) cannot be exactly the 
>entities we "intend". Indeed, such "intended" models are typically exactly 
>what we wish to be talking about when we use the language in question: The 
>natural, intended model of the language of arithmetic contains the natural 
>numbers; the natural model of an ontology for a manufacturing system might 
>well contain exactly the actual machines on the assembly line. Furthermore, I 
>must say that I am not sure what Ed means when he says that models are 
>"intrinsically intensional" or that they are "constructed from intensions". In 
>the theory of models for logical languages, this is just not the case; the 
>notion of an intrinsically intensional entity is simply not a part of the 
>theory. Moreover, I am not sure we've got enough of a grip on the notion of an 
>intensional entity beyond the idea that that distinct intensions can have the 
>same extensions. This is represented in possible world semantics by defining 
>extensions as functions from worlds to extensional entities of one sort or 
>another. It is represented in the semantics of Common Logic simply by 
>distinguishing between semantic objects and their extensions, but there is not 
>much more to be said about the nature of intensions than that  formally, at 
>any rate.
> 
>  
> So, while I think the distinction between intension and extension is 
>certainly legitimate, I am skeptical of their introduction into the modeling 
>domain in any sense beyond the well-understood (and ultimately extensional, 
>from a purely formal perspective) representations found in possible world 
>semantics or Common Logic.
> 
>  
> -chris
> 
>  
> 
> 
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