This book constitutes the refereed proceedings of the 4th European Semantic Web Conference, ESWC 2007, held in Innsbruck, Austria, in June 2007. Coverage includes semantic Web services, ontology learning, inference and mapping, social semantic Web, ontologies, personalization, foundations of the semantic Web, natural languages and ontologies, and querying and Web data models.

This volume is the proceedings of the Second International Conference on Deductive and Object-Oriented Databases (DOOD). During the last decade, deductive and object-oriented systems have received a great deal of attention, but for the most part these two fields were evolving independently of each other. Today there is a large body of work suggesting that the deductive and object-oriented paradigms complement each other. The object-oriented paradigm is characterized by its view of the data, whereby information is grouped around objects with complex internal structure accessed via methods. The...