Query Translation for Mediators over Ontology-Based Information Sources

We propose a model for providing integrated and uniied access to multiple information sources. Each source comprises: (a) an ontology i.e. a set of terms structured by a subsumption relation, and (b) a database that stores descriptions of objects using terms of the ontol-ogy. We assume that diierent sources may use diierent ontologies, i.e., diierent terminologies with terms that correspond to diierent natural languages or to diierent levels of granularity. Information integration is obtained through a mediator comprising two parts: (a) an ontology, and (b) a set of articulations to the sources, where an articulation to a source is a set of relationships between terms of the mediator and terms of that source. Information requests (queries) are addressed to the mediator whose task is to analyze each query into sub-queries, send them to the appropriate sources, then combine the results to answer the original query. We study the querying and answering process in this model and we focus on query translation between the mediator and the sources.