Role vs Group

We've been discussing the difference between roles vs groups. And I found the answer here[1]

So let me quote from[1]

"A frequently asked question is, What is the differerence between roles and groups?" Groups of users as the unit of access control are commonly provided in many access control systems. A major di erence between most implementations of groups and the concept of roles is that groups are typically treated as a collection of users and not as a collection of permissions. A role is both a collection of users on one side and a collection of permissions on the other. The role serves as an intermediary to bring these two collections together."



[1]http://csrc.nist.gov/rbac/sandhu96.pdf