This three-year award will support U.S.-France cooperative research in logic programming between Dale A. Miller of the University of Pennsylvania and Pierre Deransart of the French National Institute for Research in Computer Science and Applied Mathematics (INRIA), Rocquencourt, France. The objective of their research is to update and improve Prolog, a programming language designed from logic programming principles. Although Prolog offers many novel programming possibilities, it does not incorporate software principles of modules, types, higher-order programming, and data abstraction. The investigators will use two approaches to address these deficiencies: intuitionistic theory of logic programming and modularity in logic programming. The U.S. investigator and colleagues bring to this collaboration considerable expertise in the development of logic programming languages that encompass modular programming. This is complemented by the research at INRIA-Rocquencourt on modular programming in logic programming and application and theory of the intuitionistic theory of clauses. The project will advance development of a module system for logic programming and enhance understanding of language design with modular constraints.