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Re: [ontolog-forum] Ontology vs OWL implementation

To: Bill Andersen <andersen@xxxxxxxxxxxxxxxxx>
Cc: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Thu, 1 May 2008 20:21:57 +0200
Message-id: <p0623090fc43fb8579468@[]>
At 1:41 AM -0400 5/1/08, Bill Andersen wrote:
Hi Pat...

Hi Bill

Here we go again...

On Apr 30, 2008, at 18:08 , Pat Hayes wrote:

> At 8:21 PM +0200 4/30/08, Cati Martínez wrote:
>> Hello,
>> I'm new in the Ontology world, and maybe it has been already
>> discussed, I'm asking me the question if everything implemented in 
>> the
>> OWL language can be considered an Ontology. I guess that it's not so,
>> but it is difficult for me to say when we can say that it is or not.
> The term 'ontology' has no definition precise
> enough to answer that question. Myself, I'd be
> inclined to say yes, anything in OWL is an
> ontology. Certainly one would not expect any OWL
> tool or engine to  start distinguishing between
> 'real ontology OWL' and 'mere OWL'.


I admit the problems with coming up with anything close to a 
definition of the term "ontology" and of course no machine is going to 
be able to tell the difference.  But your position above equates (the 
referents of) "ontology" with "theory expressed in a formal 

Yes, exactly. Can you suggest any principled reason why we should not do this?

Or at least it makes them coextensional if we want to put 
that fine a point on it.

This is at least a very permissive version of Quine's position in "On 
what there is".

What has Quine got to do with it? We aren't using 'ontology' in Quine's sense. In any case, the only practical position to take on existence and quantifiers is completely at odds with Quine: to be (ie to be real, in the actual world) is NOT to be the value of a bound variable. We have to be able to quantify over possibilia, in actual ontological practice. One of the lessons of the IKRIS project is that treating quantification into "opaque" contexts by introducing rigid names for possibilia, rendering the contexts transparent, is a much better approach than the more philosopher-sanctioned technique of giving names in opaque contexts a de dicto reading. So, maybe Quine was right for philosophy, but he most certainly wasn't right for ontology engineering.

I don't think Quine would have bestowed the honor of 
existence on a lot of the referents of terms introduced in most of 
what are called "ontologies", written in OWL or not -- he reserved 
that for objects revealed by best practice in science.  Thus his 
epistemic motivation ought to appeal to you.  But certainly the 
following would not count for Quine and hopefully not for you:

      <a rdfs:subclassOf b>

That's a legal OWL theory

No, its not. The subject and object have to be legal URIreferences. This is:

extp:a rdfs:subclassOf extp:b .

And yes, that is an ontology. Its not a very interesting ontology, but I see nothing whatever to be gained by trying to give criteria to distinguish 'mere assertions' from 'real ontologies'. This kind of distinction is impossible to make precise, cannot be based on anything other than intuition or prejudice, and in any case is not the slightest use. So, to hell with it. To ignore it is good engineering, good methodology and (I submit) good philosophy. I propose to ignore it, and urge others to do the same.


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