Access control schemes come in all shapes and sizes, which makes choosing the right one for a particular application a challenge. Yet today's techniques for comparing access control schemes completely ignore the setting in which the scheme is to be deployed. In this paper, we present a formal framework for comparing access control schemes with respect to a particular application. The analyst's main task is to evaluate an access control scheme in terms of how well it implements a given access control workload (a formalism that we introduce to represent an application's access control needs). One implementation is better than another if it has stronger security guarantees, and in this paper we introduce several such guarantees: correctness, homomorphism, AC-preservation, safety, administrationpreservation, and compatibility. The scheme that admits the implementation with the strongest guarantees is deemed the best fit for the application. We demonstrate the use of our framework by evaluating two workloads on ten different access control schemes.Index Terms-access control; evaluation; state machine; parameterized expressiveness • assignUser(a,b): add UR(a, b) to the state • revokeUser(a,b): remove UR(a, b) from the state • assignPermission(a,b,c

Despite Hu's invariants were proven not to be independent nor complete long time ago, their use in computer vision applications is still broad, mainly because of their diffusion among common CV libraries and ease of use by inexperienced users. In this paper I want to investigate whether, given their mathematical flaws, they are nevertheless good enough to justify such a wide diffusion, also considering that more sophisticated tools have been developed over the years. In order to do this, I am going to test the robustness of Hu's invariants in a comparative way against the more modern wavelet invariants, in a hand gesture recognition application. Finally, I am going to discuss, basing my considerations on the experimental data, whether Hu's invariants are still a viable option for small scale, amateurish applications, or if the time has come to abandon them for more effective solutions.