Logic-based approach to semantic query optimization
ACM Transactions on Database Systems (TODS)
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In data integration systems, information sources often have various constraints such as "all houses stored at a source have a unique address." These constraints are useful in computing answers to queries. This article looks at how to describe these constraints to use them in query processing and optimization, considering the local-as-view approach under the open-world assumption in which source contents and user queries are formulated on predefined global predicates. In this approach, source contents and constraints often exist before the global predicates are designed. Constraints can be described either on the sources (local constraints) or on the global predicates (global constraints). The author explains how his team classifies various constraints; analyzes their motivations, limitations, and advantages; and looks at how to manipulate them. These insights provide a greater understanding of how to use constraints more effectively.