John, (01)
Indeed, I would say an ontology is a logical theory AND purports to be
about the real world. I can develop a nonsensical logical theory, for
example. (02)
One of the issues that we are trying to wrangle in this discussion is
perhaps to get different communities to agree to either 1) a common
definition of ontology, or 2) a typing scheme for a range of
definitions. (03)
So the ontology spectrum/semantic continuum is a pragmatic teaching
device to get the non-ontologist/non-logician technical community to
understand the components or aspects of ontology by relating it to
other notions they may know more about. (04)
If I just said "an ontology is a logical theory about a portion of the
world," eyes would glaze over and brains would turn off. (05)
Thanks,
Leo (06)
_____________________________________________
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 (07)
-----Original Message-----
From: ontology-summit-bounces@xxxxxxxxxxxxxxxx
[mailto:ontology-summit-bounces@xxxxxxxxxxxxxxxx] On Behalf Of John F.
Sowa
Sent: Thursday, January 25, 2007 8:44 AM
To: Ontology Summit 2007 Forum
Subject: Re: [ontology-summit] Defining "ontology" (08)
Leo, AJ, and Deborah, (09)
Many of the proposed definitions of ontology are much too broad.
When all the useful and important, but peripheral things are
thrown in, the difference between ontology and KR becomes blurred: (010)
AJC> I read Deborah's paper, Leo's presentation and other
> materials on ontology spectrum that were mentioned on this list.
> I found it's a nice way to view how knowledge representation
> has been evolved. If I understand correctly, the ontology spectrum
> view implies the term "ontology" is used almost as the replacement
> for "knowledge representation". (011)
It is important to distinguish two points (012)
1. What is required logically. (013)
2. What is important for other very important, but ancillary
purposes: efficient computation, development tools, etc. (014)
The question of expressiveness is important for computational
purposes, but its only logical effect is to determine how much
of the subject domain can be stated or must be omitted. Although
that may be important for many purposes, it has no effect on the
definition of what is or is not an ontology. (015)
From a strictly logical point of view, every ontology is a theory.
And a theory consists of two things: (016)
1. A base logic, whose syntactic details are irrelevant. At
the logic level, RDF, OWL, SQL, and any of the formalized
versions of UML are all subsets of Common Logic. The very
important practical differences between them are irrelevant. (017)
2. A collection of axioms that define all of the nonlogical
predicates. And by nonlogical, that means everything except
the base operators of and, or, not, some, every, etc.
Even arithmetic and set theory are part of the ontology. (018)
This gives a very crisp, very sharp definition. The supporting
tools are extremely important, but it is essential to recognize
that they are *not* part of the ontology. (019)
John Sowa (020)
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