  In the context of XACML-based access control systems, an intensive testing
activity is among the most adopted means to assure that sensible information or
resources are correctly accessed. Unfortunately, it requires a huge effort for
manual inspection of results: thus automated verdict derivation is a key aspect
for improving the cost-effectiveness of testing. To this purpose, we introduce
XACMET, a novel approach for automated model-based oracle definition. XACMET
defines a typed graph, called the XAC-Graph, that models the XACML policy
evaluation. The expected verdict of a specific request execution can thus be
automatically derived by executing the corresponding path in such graph. Our
validation of the XACMET prototype implementation confirms the effectiveness of
the proposed approach.
