Designing an Interactive Stack

We design an interactive stack in the setting of stream processing functions. The design passes through a series of abstraction levels relating different views of the stack component. The external view describes the component's input/output behaviour, the transition view captures the stepwise transitions, and the state-based view discloses the internal structure. The different descriptions can systematically be derived from the input/output behaviour following sound transformation rules. The case study exemplifies general methods for the specification and refinement of interactive components.