Ontology

Philosophy The study of what is Back to the Greeks No agreement on even the top level

Wikipedia: “In both computer science and information science, an ontology is a data model that represents a set of concepts within a domain and the relationships between those concepts. It is used to reason about the objects within that domain.”

Use of Ontology Web 2.0 or the Semantic Web Used to describe semantic relationships Models of a Domain

Ontology Elements Individuals Classes Attributes Relations Function terms Restrictions Rules Axiom Events Function terms: complex structures formed from certain relations that can be used in place of an individual term in a statement Axiom: assertions (including Rules)in a logical form that together comprise the overall theory that the ontology

Base Relations ISA - is a AKO- a kind of

Description Logic Decidable subset of First Order Logic Express objects and instances Simple axioms on relations

OWL XML based ontology language Three levels of semantics OWL lite OWL DL OWL full (not decidable) Based on RDF and RDFS Triples Base terms are URI

CYC A very large ontology Locally consistent Lennet and the goal of common sense