>KBL> Probabilistic information ought in some cases to be extremely
> > high up in a "levels of entrenchment" ordering.
>
>The level of "entrenchment" has nothing to do with level of
>importance. I would agree that a probability statement may be
>very important. But an observation that "p is true" would
>overrule a statement that p has a 95% probability of being false. (01)
The kind of probabilities that belong in an ontology won't be
overridden in this way. Instance-level probabilities don't go into
an ontology. The probabilities that go into an ontology apply to a
class of individuals. (02)
Base rates of conditions in defined populations belong in a medical
ontology. Sensitivities and specificities of diagnostic tests belong
in a medical ontology. Success rates for medical procedures performed
under given conditions by persons with given qualifications belong in
a medical ontology. (Provided, of course, that we have good data to
support the probabilistic assertions.) (03)
The probability the physician assesses that Mary Smith has breast
cancer prior to seeing the biopsy report for the lump he feels in her
breast does not belong in a medical ontology. Nor does the
probability he assesses after feeling the lump. (04)
After the biopsy definitively reveals cancerous cells in Mary's lump,
the probability that Mary has breast cancer jumps from 5% to 100%.
The assertion "Mary's lump contains cancerous cells" allows us to
prove that "Mary has breast cancer" is true. This overrides our
prior assertion "There is a 95% chance that Mary does not have breast
cancer." However, the probabilities in the ontology (5% chance that
someone with a lump in her breast has cancer; 100% chance that
someone with a lump in her breast that contains cancerous cells has
breast cancer) do not change. (05)
Probabilities in ontologies will change as we learn more about the
world. But non-probabilistic content of ontologies also changes as
we learn more about the world. (06)
>I definitely agree. But there may still be a few necessary statements,
>such as "every dog is an animal", (07)
and "Every woman with a lump in her breast that contains cancerous
cells has breast cancer." (08)
>even though there may be no clear
>set of sufficient conditions for distinguishing a dog from a wolf or
>many other kinds of animals. (09)
And just because the biopsy report says there are cancerous cells
does not mean Mary has breast cancer. (010)
Kathy (011)
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