The Role Graph Model was first introduced by Nyanchama and Osborn in 1994. It has been extended over the years to include parameterized roles, an administrative model and a delegation model. We will show how the semantics of our role graph operations differ from those of the ANSI standard. Then we will discuss how to simulate DAC, and how the underlying basic model helped us to understand and expand the model to deal with delegation. The present and future of RBAC will also be discussed.