Abstract—Vocabulary alignment is a main challenge in distributed access control as peers should understand each other’s policies unambiguously. Ontologies enable mutual understanding among peers by providing a precise semantics to concepts and relationships in a domain. However, due to the distributed nature of ontology development, ontology alignment is required to allow peers to make informed access control decisions. The alignment should be flexible and accurate to not undermine the autonomy and reliability of peers. This paper addresses the problem of ontology alignment in distributed access control by combining ontology-based trust management with a reputation system.