A modular visual model for hybrid systems

Visual description techniques are particularlyimportant for the design of hybrid systems because specifications of such systems must usuallybe discussed between engineers from a number of different disci- plines. Modularity is vital for hybrid systems not only because it allows to handle large systems, but also because hybrid systems are naturally decomposed into the system itself and its environment. Based on two different interpretations for hierarchic graphs and on a clear hybrid computation model, we develop HyCharts, two modular vi- sual formalisms for the specification of the architecture and behavior of hybrid systems. The operators on hierarchic graphs enable us to give a surprisinglysimple denotational semantics for manyconcepts known from statechart-like formalisms. Due to a verygeneral composition oper- ator, HyCharts can easily be composed with description techniques from other engineering disciplines. Such heterogeneous system specifications seem to be particularly appropriate for hybrid systems because of their interdisciplinarycharacter.