Specification and execution of policies for grid service selection

We show how a standard grid service architecture can be improved by interposing a policy enforcement engine between a calling application and the relative client stubs. Therefore, with our solution selection and invocations are not hard-coded into client applications but (declaratively) defined and enforced outside the clients; therefore they can be (de)activated and modified online. Our policies are specified using the PDL language which supports specification of preferences and prohibitions in the routing of remote invocations to Web services.