http://www.digitran.net Role Based Protection
Security administration with RBAC consists of determining the operations that must be executed by persons in particular jobs, and assigning employees to the proper roles. Complexities introduced by mutually exclusive roles or role hierarchies are handled by the RBAC software, making security administration easier.

This is commonly called "need to know" security.
Specialists in the Transcription of Medical Dictation
Role Based Protection
With role-based protection, security is managed at a level that corresponds closely to the organization's structure. Each user is assigned one or more roles, and each role is assigned one or more privileges that are permitted to users in that role.