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Thompson, John A wrote:
...Being able to partition a class into subclasses along more than
one dimension
is basic to every large ontology that we're trying to merge (I'm
guessing).
For example, we may want to partition the class Person into Male-Person
and Female-Person, and also into Adult-Person and Child-Person.
Then to create the class Girl we'll want to make it a subclass of
both
Female-Person and Child-Person. Without this ability, we'd
have to drop
one of these partitions (say, Adult-Person and Child-Person), and
stay with
a strict hierarchy where Male-Person has subclasses Man and Boy
and
Female-Person has subclasses Woman and Girl. But then any
properties
of adults have to be repeated for both Man and Woman, and any properties
of children have to be repeated for both Boy and Girl.
If you repeated these kinds of duplications throughout a global
ontology,
it would become a nightmare and a straight-jacket.
But we've all known this for years, so why are we even thinking
of doing
without multiple inheritance??
----
May I abstract from John A Thomson's example the following
formal argument, which tries to minimize resort to pragmatics?:
If the ontology contains a concept A and a concept B,
should it not also be able to contain the defined concept C := (A AND
B)
as a defined concept?
Then C has both A and B as direct superconcepts, if
neither (A subconceptOf B) nor (B subconceptOf A), -
a constellation which (as far as I see) is called a case of
"multiple inheritance" in this discussion.
If it makes sense to assert that an undefined concept D is a subconcept
of A
and is also a subconcept of B, then these two assertions can be replaced
by
(D subconceptOf (A AND B)), i.e. a primitive (undefined or partially
defined) concept
in principle needs only one direct superconcept, however, that may
be a defined concept
which needs "multiple inheritance".
The only case of "multiple inheritance" which remains in the final example
taxonomy of the Guarino/Welty paper (referred to by N. Guarino) is
"Red apple",
which seems to be equivalent to ('Red Thing' AND 'Apple').
Not yet having followed their strain of thoughts, I still wonder whether
a methodology
is attractive which advises against the assertion (for the "standard
context"),
that every country (as a primitive concept) is
(possibly among others) both a geographical region and a social entity.
Dietrich H. Fischer