Section: New Results

The Clem Workflow

Participants : Annie Ressouche, Daniel Gaffé, Joel Wanza Weloli.

Keywords: Synchronous languages, Synchronous Modelling, Model checking, Mealy machine.

This research axis concerns the theoretical study of a synchronous language le with modular compilation and the development of a toolkit (see Figure 9 ) around the language to design, simulate, verify and generate code for programs. The novelty of the approach is the ability to manage both modularity and causality. This year, we mainly work on the implementation of new theoretical results concerning the foundation of le semantics. We also design a new simulator for le programs which integrates our new approach.

First, synchronous language semantics usually characterizes each output and local signal status (as present or absent) according to input signal status. To reach our goal, we defined a semantics that translates le programs into equation systems. This semantics bears and grows richer the knowledge about signals and is never in contradiction with previous deduction (this property is called constructiveness). In such an approach, causality turns out to be a scheduling evaluation problem. We need to determine all the partial orders of equation systems and to compute them, we consider a 4-valued algebra to characterize the knowledge of signal status (unknown, present, absent, overknown). In [69] , we chosen an algebra which is a bilattice and we show that it is well suited to solve our problem. It is a new application of general bilattice theory [70] . This year, this approach has been improved, validated in clem compiler and published in [39] . Our compilation technique needs to represent Boolean equation systems with Binary Decision Diagrams (BDD) and we study and design a specific BDD library well suited to ours needs. From a practical point of view, we integrate new operators in le language (sustain until, no emit, strong abort). We focus on automata extension which can consider now three types of transition: weak transition, strong transition and normal termination transition.

Second, in clem , we generate an independent intermediate code (lec ) before specific target generations. This code represents the semantics of programs with 4-valued equation systems. In our design flow, we need to simulate programs at this level. This year, we design the cles simulator which interprets lec . The actual version don't integrate the data part of the language and we plan to do this integration.