Increased intelligence and flexibility in a distributed database system are achieved in this project using new automated reasoning algorithms. In particular, concurrency control is done by logical analysis of updates and queries to determine whether they conflict. The specific focus of the project is the design and implementation of a new database system that is fully distributed in the sense that neither concurrency control nor any other function are necessarily performed at a central site. Fully distributed concurrency control is achieved by explicit agreement between sites as to which transactions may proceed, which should be delayed, and which should be restarted. Explicit common knowledge of active transactions allows the system to adapt heuristically to changing patterns of access to the shared database. This explicit common knowledge is achieved by syntactic and semantic reasoning about queries and updates at individual sites which then execute a distributed consensus algorithm to share their conclusions. OPTIONAL: The algorithms for reasoning about query and update conflict are based on a comprehensive theory of query and update independence developed recently by the principal investigator.
