Mobility Control Via Passports

Dπ is a simple distributed extension of the π-calculus in which agents are explicitly located, and may use an explicit migration construct to move between locations. We introduce passports to control those migrations; in order to gain access to a location agents are now expected to show some credentials, granted by the destination location. Passports are tied to specific locations, from which migration is permitted. We describe a type system for these passports, which includes a novel use of dependent types, and prove that well-typing enforces the desired behaviour in migrating processes. Passports allow locations to control incoming processes. This induces major modifications to the observations which can be made of agentbased systems. Using the type system we describe these observations, and use them to build a loyal notion of observational equivalence. Finally we provide a complete proof technique in the form of a bisimilarity for establishing equivalences between systems.