We Consider as Ontologies:
Object oriented class hierarchies,
(snapshots of executing programs capture object instances)
(via their E-R or structural models)
Semi-structured databases,
(OEM <OID, label, type, value>)
(UMLS: see http://www.lexical.com)
Knowledge bases.(CYC, Ontolingua)
SKC specifically does not restrict its applicability to a purely extensional (object) or intensional (schema) definition of ontology, since its purpose is to support useful processing of extensions using intensional knowledge for all parties. To that end it is important that the intensional specifications include predicates or methods that permit the collection of extensional access to real-world objects.
We do not require ontologies to be complete specifications of a domain, but rather that usage of an ontology provide results complete with respect to the ontology.