Conference Paper

Schema merging and mapping creation for relational sources

DOI: 10.1145/1353343.1353357 Conference: EDBT 2008, 11th International Conference on Extending Database Technology, Nantes, France, March 25-29, 2008, Proceedings
Source: DBLP


We address the problem of generating a mediated schema from a set of relational data source schemas and conjunctive queries that specify where those schemas overlap. Unlike past approaches that generate only the mediated schema, our algorithm also generates view definitions , i.e., source-to-mediated schema mappings. Our main goal is to understand the requirements that a mediated schema and views should satisfy, such as completeness, preserva- tion of overlapping information, normalization, and minimality. We show how these requirements influence the detailed structure of schemas and view definitions that are produced. We introduce a normal form for mediated schemas and view definitions, show how to generate them, and prove that schemas and views in this normal form satisfy our requirements. The view definitions in our normal form use stylized GLAV mappings, for which query rewriting is easier than general GLAV mappings. We demonstrate the efficiency of query rewriting in a prototype implementation.

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Available from: Philip A. Bernstein
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    • "In the data integration research area, several efforts have also been made to automate schema merging, i.e., the automatic generation of integrated schema and the subsequent source-to-target mappings. For example, the approach proposed by Pottinger et al. is able to merge a set of relational source schemas starting from a set of conjunctive queries specifying the overlap elements between sources [29], whereas the semantic merging approach proposed in [24] creates mediated schemas by analyzing the integrity constraints and tuple generating dependencies of the sources. The Merge operator proposed by Rizopoulos et al. produces an integrated schema by analyzing all possible semantic mappings of two sources [31]. "
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    • "Our methodology outlines a definite set of likely to occur conflicts and their resolution measures in relation to the instance schema and instance data values. Fourthly, technical qualitative requirements, which serve to highlight the properties that a generic integrated schema should possess were addressed by the authors in[2][28]. A careful study of the specific approaches for multidimensional data integration attempted by the authors in[[34]seem not to have specified requirements for integration. "

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    • "More recent work on schema integration builds on the research results on semi-automatic schema matching [15] and separate matching from merging. Hence, several algorithms have been proposed to merge schemas based on a pre-determined match mapping [5], [17], [12], [18], [14]. Despite this simplification, several of these merge approaches are still not fully automatic but depend on manual intervention. "
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