Explanations and relaxations for policy conflicts in physical access control

Physical access control policies define sets of rulesthat govern people's access to physical resources such asrooms and buildings. While simple decision-precedence canbe used to reconcile different rules that result in conflictingaccess decisions, the presence of rule conflicts and other ruleanomalies can make it difficult for a policy-administrator tocomprehend and effectively manage complex policies. In this paper we are concerned with discovering conflictsand computing relaxations of access policies in order toeliminate conflicting rule instances. We propose several SATbasedencodings in which these rule conflicts and anomalies areexpressed as explanation style problems. Relaxation techniquesare in turn used to eliminate these anomalies by recommendingwhat rules have to be revoked or what permissions have to beremoved from which rules. Moreover, we discuss a relaxationstrategy that preserves most of the access constraints of theoriginal policy. Finally we provide a preliminary performancestudy of our techniques. Our approach is applicable to accesscontrol policies in general.