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By embracing the cloud computing paradigm enterprises are able to realise significant cost savings whilstboosting their agility and productivity. Yet, due mainly to security and privacy concerns, many enterprisesare reluctant to migrate the storage and processing of their critical assets to the cloud. One way to alleviatethese concerns, hence bolster the adoption of cloud computing, is to infuse suitable access control policies incloud services. Nevertheless, the complexity inherent in such policies, stemming from the dynamic nature ofcloud environments, calls for a framework capable of providing assurances with respect to the effectivenessof these policies. The work presented in this paper elaborates on such a framework. In particular, it proposesan approach for generically checking potential subsumption relations between access control policies thatincorporate the contextual knowledge that characterises an access request and which needs to be taken intoaccount for granting, or denying, the request. The proposed framework is expressed ontologically henceenabling automated reasoning, through semantic inferencing, about policy subsumption.Context-aware Policy Enforcement for PaaS-enabled Access ControlIt is generally conceded that, due to security and privacy concerns, enterprises and users are reluctant to embracethe cloud computing paradigm and hence benefit from the cost reductions and the increased flexibility or business agility that thisparadigm brings about. These concerns stem mainly from the significantly-expanded attack surfaces that result from theheterogeneous nature of cloud services and the dynamicity inherent in cloud environments. In order to alleviate these concerns,effective and flexible access control approaches are required to consider the contextual parameters that characterise data access