Metamodeling is playing an increasingly important role in object-oriented software engineering. However, most approaches use metamodels in a very pragmatic way and important conceptual questions are left open. In this paper, an object-oriented metamodeling methodology based on a formal metalanguage is introduced. The methodology allows for the description of all relevant properties of a metamodel, i. e. abstract syntax, static and dynamic semantics. Di erent kinds of instantiation relations are identi ed and a dichotomy for the classi cation of metaentities is developed. The re ection of the instantiation relations by the metalanguage is shown.

Abstract. In this paper we introduce a formal approach for the specification of safety-critical embedded systems. The specification formalisms Z and statecharts are integrated under a suitable structural model. The combined approach uses the advantages of the formalisms while avoiding their disadvantages. The different formalisms yield different, compatible views on the system: the functional view describing data and data-transformation, the reactive view, describing the system's reaction upon external stimuli, and the structural view, describing the components of the system and their interaction. The combination is discussed presenting parts of a case study: a traffic light control system. The case study is oriented at original planning documents. Besides its safety-and real-time-aspects, the case study is particularly interesting because structuring and reuse is of considerable importance in this example.

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