One of the most interesting paradigms of Ambient Intelligence is that networks of pervasive intelligent interfaces recognize our presence and mould our environment to our immediate needs. In this paper, we present an example of how an access control model such as XACML adapts its functionality at runtime to new and unforeseen requirements. In previous work, we have proposed a three levels hierarchy of artefacts to semantically represent Security and Dependability solutions so that they can be automatically applied and adapted to new context requirements. Here we apply those artefacts throughout two case studies covering (i) the representation of the XACML model and (ii) a Policy Enforcement Point. The use of these artefacts provides the interoperability, run-time reaction to changes in the application context, and the possibility to monitor the applied solutions.