During the past three years, we observe the following two trends. On theone hand, the complexity of policies is increasing from relatively simple access control models to more complex distributed and privacy aware policies. On the other hand, general purpose rst order logic based frameworks replace dedicated special purpose frameworks to give complete logical formalizations.The proposed project SIEP denes complex composite distributed access con-trol policies, including delegation and revocation of access rights, dynamic aspects such as evolving policies, trust, or belief of agents, it develops tools for verication, checking compliance, experimentation, simulation and analysis of policies, and it creates a prototype system to enforce distributed access control policies. It uses a single specication for both compile-time” verication and analysis, and run-time” resolution of authorization requests, such that techniques which thus far were used for compile-time” only, like giving explanations for access refusals, can now also be used at run-time”. SIEP combines the complementary knowledge of the University of Leuven and theUniversity of Luxembourg, establishing a new scientic relation between the two institutes.This is an application for a joint research project between Flanders andLuxemburg, falling in the scope of the international scientic cooperationbetween FWO (Flanders) and FNR (Luxemburg).