Access control systems are among the most critical of computer security components. Faulty policies, misconfigurations, or flaws in software implementations can result in serious vulnerabilities. To formally and precisely capture the security properties that access control should adhere to, access control models are usually written, bridging the gap in abstraction between policies and mechanisms. Identifying discrepancies between policy specifications and their intended function is crucial because correct implementation and enforcement of policies by applications is based on the premise that the policy specifications are correct. As a result, policy specifications represented by models must undergo rigorous verification and validation through systematic verification and testing to ensure that the policy specifications truly encapsulate the desires of the policy authors. Verifying the conformance of access control policies and models is a non-trivial and critical task, and one important aspect of such verification is to formally check the inconsistency and incompleteness of the model and safety requirements of the policy, because an access control model and its implementation do not necessarily explicitly express the policy, which can also be implicitly embedded by mixing with direct access constraints or other access control models.