From ontology to relational databases

The semantic web envisions a World Wide Web in which data is described with rich semantics and applications can pose complex queries. Ontologies, a cornerstone of the semantic web, have gained wide popularity as a model of information in a given domain that can be used for many purposes, including enterprise integration, database design, information retrieval and information interchange on the World Wide Web. Much of the current focus on ontologies has been on the development of languages such as DAML+OIL and OWL that enable the creation of ontologies and provide extensive semantics for Web data, and on answering intensional queries, that is, queries about the structure of an ontology. However, it is almost certain that the many of the semantic web queries will be extensional and to flourish, the semantic web will need to accommodate the huge amounts of existing data that is described by the ontologies and the applications that operate on them. Given the established record of relational databases to store and query large amounts of data, in this paper we present a set of techniques to provide a lossless mapping of an OWL ontology to a relational schema and the corresponding instances to data. We present preliminary experiments that compare the efficiency of the mapping techniques in terms of query performance.