Description Logic Systems with Concrete Domains: Applications for the Semantic Web

The Semantic Web initiative defines important challenges for knowledge representation and database systems. Recently, several standards for representation languages have been proposed (RDF, DAML+OIL, OWL). We briefly discuss the logical basis of these representation languages by referring to description logic (DL) inferences systems. By introducing the DL inference system Racer we demonstrate that practically usable query engines for Semantic Web representation languages are available. Then, we argue that current representation languages for the Semantic Web are not sufficient for simple and well-defined representation problems that naturally arise in the context of Semantic Web applications. In particular, we mention different kinds of algebraic constraints over various domains such as the reals or the natural numbers. We report on practical experiences with DL reasoning systems (e.g., Racer) already supporting these representation means and argue for extensions to DAML+OIL or OWL.