Quete: Ontology-based query system for distributed sources

The exponential growth of the web and the extended use of database management systems in widely distributed information systems has brought to the fore the need for seamless interconnection of diverse and large numbers of information sources. Our contribution is a system that provides a flexible approach for integrating and transparently querying multiple data sources, using a reference ontology. Global semantic queries are automatically mapped to queries local to the participating sources. The query system is capable of handling complex join constructs and of choosing the appropriate attributes, relations, and join conditions to preserve user query semantics. Moreover, the query engine exploits information on horizontal, vertical, and hybrid fragmentation of database tables, distributed over the various data sources. This optimization improves system's recall and boosts its effectiveness and performance.