Schema mappings are high-level specifications that describe the relationship between two database schemas; they are considered to be the essential building blocks in data exchange and data integration, and have been the object of extensive research investigations. Since in real-life applications schema mappings can be quite complex, it is important to develop methods and tools for understanding, explaining, and refining schema mappings. A promising approach to this effect is to use "good" data examples that illustrate the schema mapping at hand. We develop a foundation for the systematic investigation of data examples and obtain a number of results on both the capabilities and the limitations of data examples in explaining and understanding schema mappings. We focus on schema mappings specified by source-to-target tuple generating dependencies (s-t tgds) and investigate the following problem: which classes of s-t tgds can be "uniquely characterized" by a finite set...
Bogdan Alexe, Phokion G. Kolaitis, Wang Chiew Tan