  The advent of large-scale, complex computing systems has dramatically
increased the difficulties of securing accesses to systems' resources. To
ensure confidentiality and integrity, the exploitation of access control
mechanisms has thus become a crucial issue in the design of modern computing
systems. Among the different access control approaches proposed in the last
decades, the policy-based one permits to capture, by resorting to the concept
of attribute, all systems' security-relevant information and to be, at the same
time, sufficiently flexible and expressive to represent the other approaches.
In this paper, we move a step further to understand the effectiveness of
policy-based specifications by studying how they permit to enforce traditional
security properties. To support system designers in developing and maintaining
policy-based specifications, we formalise also some relevant properties
regarding the structure of policies. By means of a case study from the banking
domain, we present real instances of such properties and outline an approach
towards their automatised verification.
