Each assertion represents (asserts the existence of) a single strongly-typed relationship among the subjects that are its "role players". Each role player is a subject that plays a specific role in the relationship. The roles ("role types") themselves are subjects, and so is the type of relationship of which the relationship is an instance.

Removed strongly-typed. Subjects, such as role players, role should
be covered separately. The type of relationship of which the
relationship is an instance should be made by a separate assertion,
which itself would be a subject, since all assertions may be subjects.