Timed Migration and Interaction with Access Permissions

We introduce and study a process algebra able to model the systems composed of processes (agents) which may migrate within a distributed environment comprising a number of distinct locations. Two processes may communicate if they are present in the same location and, in addition, they have appropriate access permissions to communicate over a channel. Access permissions are dynamic, and processes can acquire new access permissions or lose some existing permissions while migrating from one location to another. Timing constraints coordinate and control both the communication between processes and migration between locations. We completely characterise those situations when a process is always guaranteed to possess safe access permissions. The consequences of such a result are twofold. First, we are able to validate systems where one does not need to check (at least partially) access permissions as they are guaranteed not to be violated, improving efficiency of implementation. Second, one can design systems in which processes are not blocked (deadlocked) because of the lack of dynamically changing access permissions.