Declarative policies for Web Service selection

We describe a modified Grid architecture that allows the specification and enforcement connection policies to Grid on Web Services. This is accomplished by interposing a policy enforcement engine between a calling application and the relative client stubs. Only service requests need be analized and filtered. Connection policies are conveniently expressed in the declarative policy specification language PPDL which allows expressing simple preferences and integrity constraints. PPDL policies are evaluated by translating them into a Logic Program with Ordered Disjunctions and calling the psmodels interpreter. This process is completely transparent to both client applications and Web/Grid services. There are clear advantages in having the connection logic expressed declaratively and externally to applications.