Equivalent classes.
Ontology(<http://example.com/ontology/Unnamed>
      Declaration(Class(:PrincipleResidentOfWhiteHouse))
      Declaration(Class(:US-President))
      AnnotationAssertion(rdfs:label :PrincipleResidentOfWhiteHouse "Principle Resident of White House"@en)
      EquivalentClasses(:PrincipleResidentOfWhiteHouse :US-President)
      AnnotationAssertion(rdfs:label :US-President "US President"@en)
) 

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