Abstract

Relational data exchange includes materializing a target instance that is consistent with the source data and the specification of the relationship between the source and the target. The properties for data exchange are exhibited by universal solutions of source instance that depends on the existence of a homomorphism. The chase procedure is used in data exchange as a tool for constructing a universal solution for a given source instance. The studies have found that for a fixed data exchange setting depending on the union of a set and weakly acyclic set, there exists a polynomial time algorithm such that every source instance it computes a universal solution. A greedy algorithm shows the desirable property of unions of conjunctive queries for data exchange. Computing certain answers for a union of conjunctive data exchange queries is done by posing the query over an arbitrary universal solution.