Chris Menzel wrote: (01)
>> My personal preference is a much stronger definition:
>
> I'm not sure it's stronger. (02)
Agreed. From a logician's point of view, my definition is so weasel
worded that it can hardly be said to be well-defined, let alone stronger. (03)
The original purpose of a "semantic web ontology", as distinct from
"logical theories", was to provide a set of terms and relationships that
would be used to markup documents to facilitate search, by allowing the
recognition of a subject in context. (04)
What I mean to eliminate is the taxonomies and thesauri that simply
introduce terms, without any effort to "define" them. They still
facilitate search, but it is not possible for a reasoner to do much with
them. (05)
>> A formal language that provides a means of definition of a term
>> using a syntax with a well-defined semantics that supports
>> (automated) reasoning is an "ontology language".
>
> Ok, let's say KIF, which is supported by the Schulz/Halcomb Tau
> reasoner. (06)
Sure. (07)
>> A model...
>
> I assume you really mean a set of sentences, and not a model in the
> model theoretic sense. (08)
Yes. That is exactly what I mean. The issue that Cati raised was
"ontologies" vs. "information models", so I took it that, in that
terminology context, they are both subtypes of "model" = a set of
sentences that describe some abstraction of someone's world. (09)
>> ...captured in that language is an "ontology" if and only if most of
>> the terms it introduces are defined in the model using the
>> definition mechanisms of the formal language (possibly including
>> references to terms that are formally defined elsewhere).
>
> Ok, let's suppose our specific KIF language has the predicates P and
> Q. I define them thus:
>
> (forall (x y) (iff (P x y) (= x y)))
>
> (forall (x y) (iff (Q x y) (not (P x y))))
>
> By your definition, this is an ontology. (Call it the "Identity and
> Difference (I&D)" ontology. :-) Maybe that's ok with you -- it's
> certainly ok with me. But I got the impression you had something more
> discriminating in mind. (010)
I am happy to call this an "ontology". That it is a "trivial" or
"degenerate" case is not a problem. It is axiomatic and it is closed.
It is vastly preferable to calling a big collection of undefined terms
with a few subsumption relationships and no other identifiable axioms an
"ontology". (011)
-Ed (012)
--
Edward J. Barkmeyer Email: edbark@xxxxxxxx
National Institute of Standards & Technology
Manufacturing Systems Integration Division
100 Bureau Drive, Stop 8263 Tel: +1 301-975-3528
Gaithersburg, MD 20899-8263 FAX: +1 301-975-4694 (013)
"The opinions expressed above do not reflect consensus of NIST,
and have not been reviewed by any Government authority." (014)
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