Complexity of answering queries using materialized views

WC study the complexity of the problem of answering queries using materinlized views, This problem has attracted a lot of attention recently because of its relevance in data integration.Previous work considered only conjunctive view definitions.We examine the consequences of allowing more expressive view definition languages.Tl~olanguagcsweconsiderforviewdefinitionsanduserqueriesare: conjunctive qucrics with inequality, positive queries, datalog, and first-order logic.We show that the complexity of the problem depcnds on whether views are assumed to store all the tuples that satisfy the view definition, or only a subset of it.Finally, we apply the results to the view consistency and view self-maintainability problems which nrise in data warehousing.