On Feb 11, 2007, at 9:58 AM, John F. Sowa wrote:
Bob and Kathy,
I agree with everything that Kathy said up to the
following sentence:
I think ontologies need to be able to represent
probabilistic relationships like these.
I certainly agree that such relationships should be
represented somewhere, but the question of where
they should be represented is another issue.
For years, I have maintained that the base ontology
(i.e., what is usually called the "upper level")
should have very few detailed axioms of any kind.
In fact, I would be delighted to have a base ontology
that contains nothing but a type hierarchy plus the
minimal constraints that everybody can agree to without
reservation. I recommend that all other information be
included in collections of axioms of the kind that Cyc
calls "microtheories".
As a general principle, all knowledge derived from
observation should be put in the microtheories, and
only the definitional information that is derived
from the most basic conventions for distinguishing
one type from another should be included in the base
ontology. In general, it is far better to leave the
base ontology underspecified than to include any axioms
that are controversial or likely to be revised and
updated as more information becomes available.
If you want to call those microtheories part of some
larger specification, which might even be called an
"extended ontology", I have no objection.
But it's essential to distinguish observational information,
which is constantly being updated and revised, from the
classifications in the base (or upper level) ontology.
John
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