Programming with Logical Queries, Bulk Updates, and Hypothetical Reasoning

This paper presents a language of update programs that integrates logical queries, bulk updates and hypothetical reasoning in a seamless manner. There is no syntactic or semantic distinction between queries and updates. Update programs extend logic programs with negation in both syntax and semantics. Users can specify bulk updates in which an arbitrary update is applied simultaneously for all answers of an arbitrary query. Hypothetical reasoning is naturally supported by testing the success or failure of an update. We describe an alternating xpoint semantics of update programs and show that it can express all nondeterministic database transformations. Current techniques of logical query evaluation can be generalized for eeective execution of updates.