This book constitutes the joint refereed proceedings of the three confederated conferences, CoopIS 2003, DOA 2003, and ODBASE 2003, held in Catania, Sicily, Italy, in November 2003.The 95 revised full papers presented were carefully reviewed and selected from a total of 360 submissions. The papers are organized in topical sections on information integration and mediation, Web services, agent systems, cooperation and evolution, peer-to-peer systems, cooperative systems, trust management, workflow systems, information dissemination systems, data management, the Semantic Web, data mining and classification, ontology management, temporal and spatial data, data semantics and metadata, real-time systems, ubiquitous systems, adaptability and mobility, systems engineering, software engineering, and transactions.