This research is primarily theoretical, building foundations and developing algorithms for various aspects of knowledge base systems. The topics addressed are: view updates, the theory of multidatabases, logic programming with null values, and efficient search of disjunctive databases. The view update problem is concerned with the appropriate translation of the user's request to update a particular view into an update of the underlying relations. Presently known solutions for relational database systems will be extended to knowledge base systems. A multidatabase is a collection of different databases that a user may wish to access simultaneously. A theoretical framework is needed to provide robustness in this complex environment. A null value is a special value that typically stands for unknown or inapplicable data. A new approach to the treatment of null values, using logic programming, is developed. Disjunctive databases allow for the representation of indefinite information. A new algorithm is developed for searching disjunctive databases. The cooperation between Towson State University and a major graduate university, the University of Maryland at College Park, will strengthen the research environment in the Department of Computer and Information Sciences at the former undergraduate institution.
