Database Reformulation
نویسندگان
چکیده
We introduce an approach to view materialization which is based on relational reformulation. In this context, we present a method for automatically discovering views of the stored relations that are not already deened yet present valuable opportunities for materialization. The proposed reformu-lation algorithm works oo-line and consists of two stages. At the rst stage, Datalog rules relevant to the queries are rewritten in a way that yields predicates of smaller arity, or merges several predicates into one. This stage produces a set of candidates for materialization. At the second stage, decisions are made on which candidates to materialize ; the criterion here is storage space available for the data. This method makes use of additional knowledge about relations, namely of the information about functional dependencies in relations. Reformulations produced by this method preserve answers to all queries and, under certain conditions, improve query-processing performance. Moreover, the reformulation algorithm is polynomial in time.
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