Hierarchical Hybrid Block Diagrams

Block diagram languages are now commonly used to design and even implement embedded systems. In the design phase, they are used to model both plant and controller, typically with continuous and discrete modeling respectively. The semantics of these languages are often vague and/or complex, which is fine for some users but leaves others puzzled by the behaviors they observe. This paper presents a pair of lean, well-defined block diagram languages corresponding to the stream and “stateful” system models. The relationship between these languages and their interoperation is discussed. In particular, the specialized stateful semantics of continuous diagrams are shown to interoperate hierarchically with discrete diagrams. The languages presented may help clarify some of the basic choices in block diagram language design, shedding light on the differences between and limitations of existing languages.