Bidirectional Constraints for Exchanging Data: Beyond Monotone Queries

In this paper, we propose to use the language of bidirectional constraints to specify schema mappings in the context of data exchange. These constraints impose restrictions over both the source and the target data, and have the potential to minimize the ambiguity in the description of the target data to be materialized. We start by making a case for the usefulness of bidirectional constraints to give a meaningful closed-world semantics for st-tgds, which is motivated by Clark’s predicate completion and Reiter’s formalization of the closed-world assumption of a logical theory. We then formally study the use of bidirectional constraints in data exchange. In particular, we pinpoint the complexity of the existence-of-solutions and the query evaluation problems in several different scenarios, including in the latter case both monotone and nonmonotone queries.