CIRC(N[P] ? (E ? P) ; P) ? N[E] ? (E ? P) E.g., KB(On)= ?x. ?On(A,x) ? On(A,B) N[On] = ( ?x. ?On(A,x) ) (E ? On) = (?x?y.x=A ? y=B ? On(x,y)) E= ?x?y.x=A ? y=B CIRC(KB;On) = (?x. ? (x=B)) ? (?x?y.On(x,y) ? x=A ? y=B) “The only thing ‘on’ something is the object denoted by A and it is on the object denoted by B, and there is at least one object that is not the same as the one denoted by B.” Systematic procedures exist for computing circumscriptions for other classes of KBs -- see the literature for details.

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