摘要：RBAC (Role Based Access Control) can support the implementation of both MAC and DAC features at the same time. This feature has been proved to be necessary in healthcare environments. The result of this mix can redefine a number of mechanisms of MEDAC (Medical Database Access Control), a security policy based on both MAC and DAC approaches. The concept of hyper node hierarchies is proposed for deriving totally ordered security levels while preserving the role hierarchy levels required satisfying particular administration needs. The advantages offered are related to the efficiency of access control, the flexibility and decentralization of administration, and the storage savings
