Reasoning about Schema Mappings

Schema mappings are an important tool in several areas of database research. Recently, the topic of reasoning about schema mappings was given attention, in particular revolving around the central concepts of equivalence and optimality. In this chapter, we survey these results. First, we introduce relaxed notions of logical equivalence and show their potential for finding optimized schema mappings. We then look at applications of these concepts to optimization, normalization, and schema mapping management, as well as the boundaries of computability. We conclude by giving a glimpse at reasoning about schema mappings in a broader sense by looking at how to debug schema mappings