Ontologies

• The Semantic Web needs a support of ontologies:
  "defines the concepts and relationships used to describe and represent an area of knowledge"
• We need a Web Ontologies Language to define:
  • the terminology used in a specific context
  • more constraints on properties
  • the logical characteristics of properties
  • the equivalence of terms across ontologies
  • etc.
• Language should be a compromise between
  • rich semantics for meaningful applications
  • feasibility, implementability

Here comes the Web Ontology Language (OWL)

• A layer on top of RDFS with additional possibilities
• Outcome of various projects (DAML, OIL)