This research addresses three important topics dealing with the foundations of knowledge bases: view updates, combining knowledge bases, and inconsistent knowledge bases. Algorithms are developed to provide solutions to several problems in this subject. 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. Algorithms that have previously been developed for stratified disjunctive databases are refined by using specialized data structures and extended to more general types of knowledge bases. Many different but related knowledge bases have been constructed in recent years. Previous research on combining knowledge bases considered primarily the case of definite deductive databases. Those algorithms are extended to more general types of knowledge bases using the stable and well-founded semantics. Sometimes a knowledge base may become inconsistent. Several different semantics have previously been proposed to define the meaning of such knowledge bases in order to localize inconsistencies. Algorithms are produced to compute answers to queries under these semantics using theorem-proving techniques. The research will be useful for the development of advanced knowledge based systems; it will also enhance the research environment at Towson State University, an undergraduate institution.
