The vision of the Semantic Web is to make web data machine processable, and rests on the premise that to do so we need to accommodate, somehow, the semantics of these data. Many technologies and methodologies are being developed within Artificial Intelligence, Databases, Software Engineering and Information Systems that can contribute towards the realization of this vision. Among those are languages for semantic annotation of Web documents, ontologies, technologies and methodologies for building multi-agent systems, semantic interoperation of programs that have been developed totally independently, technologies and methodologies for describing, searching and composing Web Services, and more.