We extend the action system formalism with a notion of objects that can be active and distributed. With this extension we can model class-based systems as action systems. Moreover, as the introduced constructs can be translated into ordinary action systems, we can use the theory developed for action systems, especially the refinement calculus, even for class-based systems. We show how inheritance can be modelled in different ways via class refinement. Refining a class with an other class within the refinement calculus ensures that the original behavior of the class is maintained throughout the refinements. Finally, we show how to reuse proofs and entire class modules in a refinement step.