not - Winter 2006 COSC-6490B: Issues in Information...

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Unformatted text preview: Winter 2006 COSC-6490B: Issues in Information Integration Godfrey p. 1 Negation Datalog with Negation Okay. Let us add not to the Datalog language (Datalog ). E.g., cousin ( X, Y ) grandparent ( P, X ), grandparent ( P, Y ), X negationslash = Y , not sibling ( X, Y ). We only allow use of not on the right-hand side of the . The intuitive meaning of not is quite clear. How to handle it formally is far from clear. What are the models of a Datalog database? What should the proof procedure be for Datalog ? This not is not logical negation ( )! Winter 2006 COSC-6490B: Issues in Information Integration Godfrey p. 2 Safeness Extended for Datalog We require that Datalog programs be safe . We need to extend the definition of safeness for Datalog : Any variable that appears either in the head atom of the rule (on the left-hand side) or in a negated atom must also appear in a non-negated atom in the body (on the right-hand side). Thus, h ( X 1 , . . . , X k ) b 1 ( Y 1 , . . . , Y j 1 ) , . . . , b m ( Y j m 1 , . . . , Y j m ) , not d 1 ( Z 1 , . . . , Z j 1 ) , . . . , not d n ( Z j n 1 , . . . , Z j n ). is safe if ( { X 1 , . . ., X k } { Z 1 , . . . , Z j n } ) { Y 1 , . . . , Y j m } Winter 2006 COSC-6490B: Issues in Information Integration Godfrey p. 3 Non-Monotonicity...
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not - Winter 2006 COSC-6490B: Issues in Information...

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