Abstract

A practical heterogeneous, distributed multidatabase system must answer queries efficiently. Conventional query optimization techniques are not adequate here because these techniques are dependent on the database structure, and rely on limited information which is not sufficient in complicated multidat abase queries. This paper presents an automated approach to reformulating query plans to improve the efficiency of multidatabase queries. This approach uses database abstractions, the knowledge about the contents of databases, to reformulate a query plan into less expensive but semantically equivalent one. We present two algorithms. The first algorithm reformulates sub queries to individual databases, the second algorithm extends the first one and reformulates the entire query plan. Empirical results show that the reformulations can provide significant savings with minimal overhead. The reformulation …

Date

December 1, 1993

Authors

Chun-Nan Hsu, Craig A Knoblock

Book

Proceedings of the second international conference on Information and knowledge management

Pages

423-432