This book constitutes the thoroughly refereed postproceedings of the Second International Workshop on Semantic Web and Databases, SWDB 2004, held in Toronto, Canada in August 2004 as a satellite workshop of VLDB 2004.

The 14 revised full papers presented together with 2 papers by the invited keynote speakers were carefully selected during two rounds of reviewing and improvement from 47 submissions. Among the topics addressed are data semantics, semantic Web services, service-oriented computing, workflow composition, XML semantics, relational tables, ontologies, semantic Web algebra, heterogeneous data sources, context mediation, OWL, ontology engineering, data integration, semantic Web queries, database queries, and peer-to-peer warehouses.