A Modular Development of the Denotational RSL Concurrency Model

The concurrency features of the RAISE specification language RSL are based on an adaptation of Hennessy’s model of acceptance trees [Hen85]. An extension was necessary to meet requirements of RSL. A paper by Bolignano and Debabi [BD92] describes this extension. We will revisit this extension, now formalising the relationship between the basic model and its extension in a rigorous way. We will show general mechanisms how to extend languages and models in order to preserve properties of the basic model. Our mechanisms are applied to the basic model — which is extended in two steps — preserving properties such as behaviour and static domain constraints. The framework of language extension which will be used here aims at supporting experimentation with and explorationof semantics. In this case, a semantic model for concurrent languages is investigated. An application could be an investigation into the suitability of a semantic model for a given language which has to be defined formally.