An algorithm for answering queries efficiently using views

Algorithms for answering queries using views have been used in query planning to answer queries posed to knowledge bases, databases, and information systems. However, these algorithms do not scale well when the number of views increases. Three known algorithms, the bucket algorithm, the inverse-rules algorithm and an algorithm suggested by Leser have been used to reformulate queries before generating their answers. The bucket algorithm, predominantly used to reformulate queries, generates a candidate rewriting to a query using views, and checks that the rewriting is contained in the original query. An exponential conjunctive-query-containment-test needs to be performed to check each candidate rewriting. Using a few extra buckets (shared-variable-buckets), we show how we can avoid the conjunctive-query-containment-test. This paper presents a scalable query rewriting algorithm the shared-variable-bucket(SVB) algorithm. Experimental results demonstrate its superiority over other known algorithms.