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C00002 00002	circum.com[w83,jmc]	Making circumscription computable
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circum.com[w83,jmc]	Making circumscription computable

	To compute the circumscription formulas for a
data base every time it is used or even
every time it is changed is too much.  Therefore we
need a way of pre-computing, so that the database
can say it doesn't know one fact or concludes
another by circumscription.
For example, we need to be able to conclud promptly
that Tweety can fly, and that it cannot be
determined whether Nixon is a pacifist or whether
X lives in Toronto with his wife or in Vancouver
where his employer is located.

	We also need a way of saying that Tweety's color
is irrelevant to his being able
to fly or of being able to jump to that conclusion.  We can
perhaps jump to that conclusin by a circumscription
taking into account available meta-information
in the database.