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An Approach to Designing Safety Critical Systems using the Unified Modelling Language

In this paper an approach to using the UML for developing safety critical systems is presented. We describe how safety analysis may be performed on a UML system model and how this analysis can derive safety requirements for classes in the system. We show how these requirements can be expressed in the form of safety contracts using the OCL. This makes it possible to reason about the safety of individual elements of the UML model and thus makes it easier to safely change the UML design, as well as facilitating maintenance and reuse of classes or components in the system. A tool is also described which has been developed to automate some aspects of this analysis.