An action system approach to the steam boiler problem

This paper presents an approach to the specification of control programs based on action systems and refinement. The system to be specified and its physical environment are first modelled as one initial action system. This allows us to abstract away from the communication mechanism between the two entities. It also allows us to state and use clearly the assumptions that we make about how the environment behaves. In subsequent steps the specifications of control program and the environment are further elaborated by refinement and are separated. We use the refinement calculus to structure and reason about the specification. The operators in this calculus allow us to achieve a high degree of modularity in the development.