Most ontologies use the same basic set of components. The first four are the "main" ones.

• Individuals
  • Instances of a class
• Classes (or "kinds")
  • A kind of thing that can have properties (nouns)
• Attributes
  • Properties that members of a class can have
• Relations
  • How classes or individuals can relate to others
• Restrictions
  • What must be true about something to be valid
• Rules/Axioms
  • Logical statements describing inferences that can be made
• Events
  • Changing of attributes or relations

Source

Ontology components - Wikipedia

Related Notes

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Ontology Language