Query Answering Systems in the Semantic Web

In this paper a new query answering system is presented for querying knowledge bases in the Semantic Web. The implementation follows the DAML+OIL Query Language Abstract Speci cation (DQL) and supports acyclic conjunctive queries. The system uses a Description Logic (DL) reasoner to answer the queries and the conjunctive queries are transformed into DL retrieval or boolean queries. After the introduction to the new DQL implementation, a comparison with other systems follows. This includes the recently introduced new Racer Query Language (nRQL), the DQL implementation provided by the Knowledge Systems Laboratory of the Stanford University and a DQL implementation provided by the University of Maryland, Baltimore County. The paper highlights and compares the di erent approaches of these systems.