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Re: [ontolog-forum] Terminologies and Ontologies

To: ontolog-forum@xxxxxxxxxxxxxxxx
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Sat, 30 Apr 2011 23:19:32 -0400
Message-id: <4DBCD144.20409@xxxxxxxxxxx>
Doug and Rich,    (01)

I strongly agree with the following point:    (02)

> Ontologies used in productive systems only cover the needed domains.
> This is why the standard definition used by professionals is stated
> so as to allow the restriction of ontologies to a single domain or set
> of them.    (03)

But little words like 'a' or 'an' are very significant:    (04)

> "Ontology is a general theory about some aspect of the world, its
> subdomains, entities and relationships."    (05)

I agree, but with the article 'an' at the beginning.    (06)

The word 'ontology' by itself refers to the subject matter --
the branch of philosophy devoted to the study of existence
and the methodologies for formulating such theories.    (07)

> "A formal ontology is a formal theory of some aspect of world, its
>  subdomains, entities and relationships."    (08)

I agree.    (09)

> What can you do with two ontologies that, while discernibly different,
> both describe what exists in the same domain?    (010)

Determine the kinds of problems for which one or the other might be
more useful.    (011)

For example, quantum electrodynamics (QED) is the most accurate theory
of physics that is currently well established.  There are more exotic
ones, but they're still highly speculative.    (012)

However, QED requires high-powered math, which can be very difficult
to calculate.  For most practical problems, physicists and engineers
use one or another of the following:    (013)

  1. Newtonian mechanics, which is the simplest and which generates
     answers for most human-scale phenomena that are well within the
     limits of accuracy of most measuring instruments.    (014)

  2. Special relativity for phenomena at high speeds.    (015)

  3. General relativity for phenomena that involve astronomical
     distances or high gravitational fields.    (016)

  4. Ordinary quantum mechanics, for phenomena for which it is
     sufficiently accurate.    (017)

This, of course, is rather high-powered physics, but the issues are
similar for more mundane kinds of problems.  You use the theory that
is known to be reliable for the kinds of applications you have.    (018)

Furthermore, you might need different theories for different parts
of the same system.  For cars and people, Newtonian mechanics is
as accurate as needed.  But cars have components that may need
different theories -- for example, the combustion inside the
engine or the electrons flowing through transistors in a computer.    (019)

You can use different theories for different components -- as long as
they produce compatible results at the interfaces.    (020)

John    (021)

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