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 P
v
which uses only views as EDB predicates and (i) produces a subset of the answers that P produces and (ii) any other program P′
v
over the views with property (i) is contained in P
v
? In this paper we investigate the problem in the case of disjunctive view definitions.
This work has been partially supported by the Greek General Secretariat of Research and Technology under the project “Logic
Programming Systems and Environments for developing Logic Programs” of ΠENEΔ′95, contract no 952.