This book constitutes the refereed proceedings of the Second International Semantic Web Conference, ISWC 2003, held at Sanibel Island, Florida, USA in October 2003.The 58 revised full papers presented were carefully reviewed and selected from numerous submissions. The papers are organized in topical sections on foundations; ontological reasoning; semantic Web services; security, trust, and privacy; agents and the semantic Web; information retrieval; multimedia; tools and methodologies; applications; and industrial perspectives.