Ontologies have gained significant attention due to recent developments in the Semantic Web, as technologies are now being provided that enable the use of ontologies in information systems. Beginning with the fundamental concepts and ideas of ontologies that originate from philosophy and linguistics, the book presents the current state of the art in the field of supporting technologies from Semantic Web research and highlights promising application areas. The book is aimed at all readers who have a basic interest in ontologies as part of modern information technologies and wish to gain an overview and quick entry into the field.