Executable HybridUML and Its Application to Train Control Systems

In this paper, the authors introduce an extension of UML for the purpose of hybrid systems modeling. The construction uses the profile mechanism of UML 2.0 which is the standard procedure for extending the Unified Modeling Language. The “intuitive semantics” of the syntactic extension is based on the semantics for hierarchic Hybrid Automata, as suggested by Alur et. al. In contrast to Alur’s formalism, HybridUML allows to label transitions not only with conditions and assignments, but also with signals. Furthermore, our approach associates formal semantics by definition of a transformation from HybridUML specifications into programs of a “low-level” language which is both executable in hard real-time and semantically well-defined. When compared to approaches assigning semantics directly to the high-level constructs of a formal specification language, the transformation approach offers two main advantages: First, semantics can be more easily adapted to syntactic extensions by extending the transformation in an appropriate way. Second, all models are automatically executable, since the low-level language is.