Answering Queries Using Materialized Views with Disjunctions

. We consider the problem of answering datalog queries using materialized views. More specifically, queries are rewritten to refer to views instead of the base relations over which the queries were originally written. Much work has been done on program rewriting that produces an equivalent query. In the context of information integration, though, the importance of using views to infer as many answers as possible has been pointed out. Formally, the problem is: Given a datalog program P is there a datalog program Pv which uses only views as EDB predicates and (i) produces a subset of the answers that P produces and (ii) any other program P 0 v over the views with property (i) is contained in Pv? In this paper we investigate the problem in the case of disjunctive view definitions. 1 Introduction A considerable amount of recent work has focused on using materialized views to answer queries [1, 7, 5, 12, 16, 13, 4]. This issue may arise in several situations, e.g., if the relations men..