Logic Programming and Deductive Databases

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9300691 Minker This is the first year funding of a three-year continuing award. Two related topics, logic programming and deductive databases are to be studied. In the former, the semantics of extended disjunctive logic programs with logical negation and negation-by- default are to be developed. Model theoretic, proof theoretic and fixpoint semantics are to be devised for this class of programs. Alternative rules for negation-by-default are to be considered. Work in extended disjunctive logic programming is related to commonsense and nonmonotonic reasoning. It will extend the expressive power of logic programming and will permit users to naturally combine logical negation and negation-by-default in one theory and to compute in that theory. In deductive databases topics to be studied are: alternative theories for disjunctive normal and extended deductive databases; the view update problem in disjunctive theories; cooperative answering; and combining multiple databases with priorities among atoms. Work in deductive databases will permit computation in situations where data is indefinite. This is important for databases containing imprecise information (e.g., medical). A formal theory of database updates is to be developed for disjunctive databases. Cooperative answering systems will provide meaningful answers to user queries in databases and will permit queries to be relaxed when there are no answers to the original query. ***