Ontology components
Contemporary ontologies share many structural similarities, regardless of the language in which they are expressed. Most ontologies describe individuals (instances), classes (concepts), attributes, and relations.
Overview
Common components of ontologies include:
Individuals: instances or objects (the basic or "ground level" objects)
Classes: sets, collections, concepts, types of objects, or kinds of things.
Attributes: aspects, properties, features, characteristics, or parameters that objects (and classes) can have
Relations: ways in which classes and individuals can be related to one another
Function terms: complex structures formed from certain relations that can be used in place of an individual term in a statement
Restrictions: formally stated descriptions of what must be true in order for some assertion to be accepted as input
Rules: statements in the form of an if-then (antecedent-consequent) sentence that describe the logical inferences that can be drawn from an assertion in a particular form