I Like the spirit of what John says here, insofar as a thing called O
might be formal or it might be informal. (01)
I think that arguing over what the word 'ontology' should or should not
mean is not a good place to start. (02)
Start instead by identifying useful things that seem to fit some
people's definition of 'ontology'. Like for example, there are 'things'
that consist of:
* a set of concepts (scoped around some subject matter in some real or
imagined world)
* a set of specifications of meanings for the concepts
* a set of terms for those concepts (03)
I have found that just about anything that anyone has ever called an
ontology fits this description. Some are formal, some aren't some are
logical theories, some are not. Some have this that or the other
property, some don't. (04)
So this would be a good place to start of a definition of an ontology
(IMHO). (05)
Note that the simple logical theory ChrisW used, does not fit this
description. (06)
Lets identify the most useful set of properties that we want our 'thing'
to have, and then simply say that this is what WE are talking about when
we say 'ontology'. (07)
One property that have been mentioned is:
* is a logical theory (08)
In years gone by, another property was:
* intended to be shared
-- which bring purpose of the thing into the definition of the thing,
somewhat problematic. (09)
Most of us in this group would require it to be a logical theory.
BTW: This is different from saying every logical theory is an ontology,
however.
Some of the postings suggest that there is confusion on this point. (010)
Mike (011)
==========================
Michael Uschold
M&CT, Phantom Works
425 373-2845
michael.f.uschold@xxxxxxxxxx
========================== (012)
----------------------------------------------------
COOL TIP: to skip the phone menu tree and get a human on the phone, go
to: http://gethuman.com/tips.html (013)
-----Original Message-----
From: John F. Sowa [mailto:sowa@xxxxxxxxxxx]
Sent: Sunday, January 28, 2007 9:21 AM
To: Ontology Summit 2007 Forum
Subject: Re: [ontology-summit] ontology as logical theory? (014)
Bill, Leo, and Chris M & W, (015)
I mostly agree with Chris M, but I'd like to add a condition that
distinguishes an ontology from an arbitrary theory: (016)
A theory O expressed in a language L is an ontology iff O
defines one or more types of entities, and for each defined
type T, O shall determine whether any individual x is or
is not an instance of T. (017)
If L is a formally defined version of logic, then O is called
a _formal ontology_; otherwise, O is an _informal ontology_. (018)
Note that this definition allows an ontology to be distinguished from an
arbitrary theory. For example, the following statements constitute a
theory, but not an ontology, because they do not state conditions for
defining any types: (019)
There is a man named Bob who is taller than a man named Joe. (020)
Every individual named Tiny Tim is shorter than any
individual named Big Bad Bob. (021)
No letters in circular envelopes are delivered on Tuesdays. (022)
Note that this theory could be converted into an ontology if it included
a definition of the type LoopyLetter as a letter enclosed in a circular
envelope. That single definition would be sufficient to make it an
ontology, but not a good one, since it contains statements that are
irrelevant to the defined type. (023)
I certainly agree that some ontologies are better than others and that
we should bestow honors and shame where appropriate.
But that can be done by putting little words like "good" or "bad" in
front of the word "ontology". (024)
The conditions of goodness and badness are independent of whether the
ontology is formal or informal. We could have some carefully written
good informal ontologies, and some bad formal ontologies.
But to be interpretable by a computer, the ontology must be formal. (025)
John Sowa (026)
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