Models of Computation

Classical models of computation in computer science, rooted in Turing-Church theories for non-concurrent systems, and in nondeterministic transition systems and process algebras for concurrent systems, do not handle temporal dynamics well. Extending these theories to embrace metric time, to handle multiform time, and to provide concurrency models that match better the concurrency of the physical world is a central CPS problem. For example, when considering software components, the classical software-engineering notion of objects, which interact with one another through procedure calls, might be replaced or supplemented with an "actor-oriented" component model. Actors interact with one another through input-output stimuli rather than procedure calls. An actor reacts to input stimulus by changing state and providing output stimulus that other actors can react to. Many distinct models of computation can be built around this basic notion of actors.