Negation as Failure
Keith L. Clark
A query evaluation process for a logic data base comprising a set of clauses is described. Its is essentially a Horn clause theorem prover augmented wih a special negation as failure inference rule whereby ~P can be inferred if every possible proof of P fails. We show how the rule only allows us to conclude negated facts that could be inferred from the completed date base, a data base of relation defintions and equality schemas that we consider is implicitly given by the data base of clauses.
KEYWORDS: Completed data base, equality theory
First Published in: Logic and Data Bases, (eds Gallaire and Minker), 1978.
for a pdf version of the paper (NegAsFailure.pdf, 736K bytes).