There are two ways of looking at Access Control. One is easy, with a
direct relation to the resources being managed. The other is advanced,
but like putty in the hands of administrators; moreover, it is highly
efficient. Efficiency matters; it allows us to enforce access control
everywhere, with no experienced discomfort. We derive the efficient
model from the one that is easy to use.
Our work on Identity is ultimately for controlling access to
online services. We now introduce our thoughts on Access Control.
The whole story is complex, but an analogy to the phone system can
help to explain it.