Here's another problem I've been facing & failing to solve:
Take these rules:
[1] pet of teacher isa mammal
[2] dog isa mammal
[3] poodle isa mammal
Now, to these, I want to somehow be able to state that (a) the
pet can just be-a dog, and not necessarily any particular breed
of dog, and (b) the pet can't just be-a mammal and not some
particular species of mammal.
One of (a) or (b) is presumably the default option, so my
question is how to state the nondefault option.
--And.
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