A conservative extension of synchronous data-flow with state machines

Abstract

This paper presents an extension of a synchronous data-flow language such as Lustre with imperative features expressed in terms of powerful state machine à la SyncChart. This extension is fully conservative in the sense that all the programs from the basic language still make sense in the extended language and their semantics is preserved.From a syntactical point of view this extension consists in hierarchical state machines that may carry at each hierarchy level a bunch of equations. This proposition is an alternative to the joint use of Simulink and Stateflow but improves it by allowing a fine grain mix of both styles.The central idea of the paper is to base this extension on the use of clocks, translating imperative constructs into well clocked data-flow programs from the basic language. This clock directed approach is an easy way to define a semantics for the extension, it is light to implement in an existing compiler and experiments show that the generated code compete favorably with ad-hoc techniques. The proposed extension has been implemented in the ReLuC compiler of Scade/Lustre and in the Lucid Synchrone compiler.