I agree. The terminology is not important. What's important is the
axiomatization. (01)
In description logics in general (and OWL), classes and restricted
classes and any way you can construct in the language to refer to
instances are taken to be intensional descriptions, all of which are
different, even though they may pick out the same extension (i.e.,
instances). (02)
Now there are some wrinkles: when you use the OWL equivalence
relations, you are saying that the two things that are equivalent are
extensionally equivalent. This is perfectly fine. "The Morning Star" ==
"The Evening Star" are only extensionally equivalent (i.e., the two
distinct descriptions pick out "Venus" in their extension). There is NO
intensional equivalence, i.e., other properties that the intensional
description "The Morning Star" has (like being visible at dawn) does
not mean that intensional description "The Evening Star" has them, and
vice versus). (03)
Leo (04)
_____________________________________________
Dr. Leo Obrst The MITRE Corporation, Information Semantics
lobrst@xxxxxxxxx Center for Innovative Computing & Informatics
Voice: 703-983-6770 7515 Colshire Drive, M/S H305
Fax: 703-983-1379 McLean, VA 22102-7508, USA (05)
-----Original Message-----
From: ontac-dev-bounces@xxxxxxxxxxxxxx
[mailto:ontac-dev-bounces@xxxxxxxxxxxxxx] On Behalf Of Chris Menzel
Sent: Friday, January 20, 2006 10:25 AM
To: ONTAC Taxonomy-Ontology Development Discussion
Subject: Re: [ontac-dev] Type vs. Class -- Please vote (06)
On Fri, Jan 20, 2006 at 02:45:07AM -0500, Pat Cassidy wrote:
> I would like to get a sense of this group on a terminological
> question. If you have any preference at all, please send me a note
> directly. (07)
That the more-or-less-kinda-sorta synonymous term in the W3C languages
is "Class" seems to me settle the issue. Indeed it seems to
me downright perverse to consider an alternative, give how very very
little, hangs on the choice. (As noted, in my view, nothing whatever
hangs on the choice, since we can specify the desired meaning of the
chosen term with judiciously selected axioms.) W3C is laying the
foundations for the Semantic Web, and so OWL/RDF(S) and their ilk, for
better or worse, are the way of the world. I doubt this group will be
taken seriously by the very large, very influential W3C community if it
chooses to depart from established, standard W3C terminology for this
fundamental concept. (08)
2-cents-edly yours, (09)
-chris (010)
ps: Note also that, as desired here, classes in RDF(S)/OWL are not
extensional by default, that is, it does not follow in those languages
that classes are identical if the have the same instances. (011)
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