Graph-based specification formalisms for Access Control (AC) policies
combine the advantages of an intuitive visual framework and of
a rigorous semantical foundation. A security policy framework
specifies a set of (constructive) rules to build the system states and
sets of positive and negative (declarative) constraints to specify
wanted and unwanted substates. Models for AC (e.g. role-based,
lattice-based or discretionary) have been specified in this
framework elsewhere and the problem of evolution and integration of policies
has been tackled. Here we address the problem of inconsistent policies within
this framework. Using formal properties of graph transformations, we can
systematically detect inconsistencies between two (declarative) constraints,
between two (operational) rules and between a rule and a
constraint and lay the foundation for their
resolutions.