What is an Ontology?

In 1992 Tom Gruber proposed the following definition "An ontology is a specification of a conceptualization" [4]. Several variants exist that usually add adjectives further describing the specification (e.g., "formal", "explicit") or the conceptualization (e.g., "shared") (see discussion of related work in Section 5). These definitions are not helpful because they violate one of the basic rules for good definitions: the defining statement (the definiens) should be clearer than the term that is defined (the definiendum). As long as "conceptualization" is murkier than "ontology", any attempt of defining "ontology" as a kind of "specification of a conceptualization" is an intellectual placebo: it makes us feel like it provides a better grasp of the nature of ontologies, but there is no intellectual progress, because it lacks explanatory value (see Section 2 for details). Given the difficulties in defining "ontology" one may come to the conclusion that a proper definition is not really needed.