Technical Report CS0421

Title: The Relational Algebric Operator NOT
Authors: Yoav Raz
Abstract: Some Relational Algebra (RA) operations give the exact meaning of Natural Language (NL) constructs when both Entity-sets and Relationship-sets are represented as relations (e.g. relativization and the natural-join, coordination and the union and intersection, universal-quantifiers and setcomparison, and the generalized-division, restriction and the selection and theta-join). The proposed NOT (COMPLEMENT) operator enables to express NL negation as a single operation in "closed world" databases. It can replace the subtraction, which does not have a direct linguistic analog, and is useful being implemented in an environment which supports NL or NL-like queries using RA.
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