A stratified first order logic approach for access control

Modeling information security policies is an important problem in many domains. This is particularly true in the health care sector where information systems often manage sensitive and critical data. This paper proposes to use non-monotonic reasoning systems to control access to sensitive data in accordance with a security policy. In the first part of the paper, we propose an access control model which overcomes several limitations of existing systems. In particular, it allows to deal with contexts, and to represent the two main kinds of privileges: permissions and prohibitions. This model will then be formally encoded using stratified (or prioritized) first order knowledge bases. In the second part of the paper, we discuss the problem of conflicts due to the joint handling of permissions and prohibitions. We show that approaches proposed for solving conflicts in propositional knowledge bases are not appropriate for handling inconsistent first order knowledge bases.