Ontologies And The Semantic Web

Ontologies have become a prominent topic in Computer Science where they serve as explicit conceptual knowledge models that make domain knowledge available to information systems. They play a key role in the vision of the Semantic Web where they provide the semantic vocabulary used to annotate websites in a way meaningful for machine interpretation. As studied in the context of information systems, ontologies borrow from the fields of symbolic knowledge representation in Artificial Intelligence, from formal logic and automated reasoning and from conceptual modeling in Software Engineering, while also building on Web-enabling features and standards.Although in Computer Science ontologies are a rather new field of study, certain accomplishments can already be reported from the current situation in ontology research. Web-compliant ontology languages based on a thoroughly understood theory of underlying knowledge representation formalisms have been and are being standardized for their widespread use across the Web. Methodological aspects about the engineering of ontologies are being studied, concerning both their manual construction and (semi)automated generation. Initiatives on "linked open data" for collaborative maintenance and evolution of community knowledge based on ontologies emerge, and the first semantic applications of Web-based ontology technology are successfully positioned in areas like semantic search, information integration, or Web community portals.This chapter will present ontologies as one of the major cornerstones of Semantic Web technology. It will first explain the notion of formal ontologies in Computer Science and will discuss the range of concrete knowledge models usually subsumed under this label. Next, the chapter surveys ontology engineering methods and tools, both for manual ontology construction and for the automated learning of ontologies from text. Finally, different kinds of usage of ontologies are presented and their benefits in various application scenarios illustrated.