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Concept types

		class
		relation
		attribute
		instance

Relation types

A     B		B is a subclass of A
A     B		B is an instance of A
A     B		B is an instance of A, A is a subclass of relation
A     B		both A and B are instances of relation, B is a subrelation of A
A     B		B is an instance of A, A is a subclass of attribute
A     B		both A and B are instances of attribute, B is a subattribute of A