Today sophisticated concepts, languages and frameworks exist, that allow implementing powerful fine grained access control systems for protecting Web Services and spatial data in SDIs. Especially rule based access control systems provide the capabilities to define and enforce expressive, fine grained access rights or restrictions respectively. Having powerful and complex access control policies in place introduces a new challenge. It is essential that the policy defining the semantics of an access control system can be easily and securely administrated. In this paper a very general and powerful administrative model, the Layered Administration Model (LAM), will be introduced. The LAM intends to support an easy, secure and tractable administration of complex spatial access control policies as found in SDIs. Categories and Subject Descriptors H.4 [Information Systems Applications]: General Terms Security, Standardization, Languages, Theory, Verification. Keywords Access control, Administ...