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Schema mapping and query translation in heterogeneous peer-to-peer XML databases Chang, Elaine Qing

Abstract

In a peer-to-peer data management system, the peers may have heterogeneous schemas, and no mediated global schema. To' facilitate data exchange, we assume each entering peer provides correspondences between its schema and a small number of other peer schemas. We study the problem of schema mapping and query translation in the context of heterogeneous XML schemas, featuring data/schema conflict. We develop an algorithm for inferring precise mapping rules from informal schema correspondences. We define the semantics of query answering in this setting and develop an algorithm for query translation. Our translation can work both along and against the direction of mapping rules and can handle an expressive fragment of XQuery. We have developed the HePToX heterogeneous P2P XML data management system on top of the Emulab, a large scale P2P network emulation testbed, incorporating our ideas and results. We describe our implementation strategy and report the results of an extensive set of experiments on HePToX on both synthetic and real data sets, demonstrating its utility and scalability.

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