Querying the Semantic Web with RQL

  • Authors:

  • G. Karvounarakis;A. Magganaraki;S. Alexaki;V. Christophides;D. Plexousakis;M. Scholl;K. Tolle

  • Affiliations:

  • Institute of Computer Science, FORTH, Vassilika Vouton, P.O. Box 1385, GR 711 10 Heraklion, Greece;Institute of Computer Science, FORTH, Vassilika Vouton, P.O. Box 1385, GR 711 10 Heraklion, Greece;Institute of Computer Science, FORTH, Vassilika Vouton, P.O. Box 1385, GR 711 10 Heraklion, Greece;Institute of Computer Science, FORTH, Vassilika Vouton, P.O. Box 1385, GR 711 10 Heraklion, Greece;Institute of Computer Science, FORTH, Vassilika Vouton, P.O. Box 1385, GR 711 10 Heraklion, Greece;CEDRIC/CNAM, 292 Rue St Martin, 75141 Paris Cedex 03, France;Johann Wolfgang Goethe-University, Robert-Mayer-Strasse 11-15, P.O. Box 11 19 32, D-60054 Frankfurt/Main, Germany

  • Venue:
  • Computer Networks: The International Journal of Computer and Telecommunications Networking - Special issue: The Semantic Web: an evolution for a revolution
  • Year:
  • 2003

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Abstract

Real-scale Semantic Web applications, such as Knowledge Portals and E-Marketplaces, require the management of voluminous repositories of resource metadata. The Resource Description Framework (RDF) enables the creation and exchange of metadata as any other Web data. Although large volumes of RDF descriptions are already appearing, sufficiently expressive declarative query languages for RDF are still missing. We propose RQL, a new query language adapting the functionality of semistructured or XML query languages to the peculiarities of RDF but also extending this functionality in order to uniformly query both RDF descriptions and schemas. RQL is a typed language, following a functional approach a la OQL and relies on a formal graph model that permits the interpretation of superimposed resource descriptions created using one or more RDF schemas. We illustrate the syntax, semantics and type system of RQL and report on the performance of RSSDB, our persistent RDF Store, for storing and querying voluminous RDF metadata.