Roles not only have a player Entity but also a "scoper", which is what recognized the player in this Role. For example, the Person playing the Patient role does that in the scope of a hospital (Entity), likewise the hospital recognized the doctor (Entity) as a surgeon (Role). Thus, Roles establish durable relationships. In the world of things Role includes very basic ontological and mereological relationships, for example, a wheel (Entity) plays a part (Role) of a car (Entity), the whole car scopes the "part" role played by the wheel. Other fundamental types of Role are the generalization/specialization relationship, the group/member relationship, the container/content relationship, and the mixture/ingredient relationship.