Synthesizing safe state machines from Esterel

Abstract

Esterel and Safe State Machines (SSMs) are synchronous languages dedicated to the modeling of embedded reactive systems. While Esterel is a textual language, SSMs are based on the graphical Statecharts formalism. Statecharts are often more intuitive to understand than their textual counterpart, and their animated simulation can help to visualize subtle behaviors of a program. However, in terms of editing speed, revision management, and meta-modeling, the textual nature of Esterel is advantageous. We present an approach to transform Esterel v5 programs into equivalent SSMs. This permits a design flow where the designer develops a system at the Esterel level, but uses a graphical browser and simulator to inspect and validate the system under development.We synthesize SSMs in two phases. The first phase transforms an Esterel program into an equivalent SSM, using a structural translation that results in correct, but typically not very compact SSMs. The second phase iteratively applies optimization rules that aim to reduce the number of states, transitions and hierarchy levels to enhance readability of the SSM. As it turned out, this optimization is also useful for the traditional, manual design of SSMs. The complete transformation has been implemented in a prototypical modeling environment, which allows to demonstrate the practicality of this approach and the compactness of the generated SSMs.

Scenario-based verification in presence of variability using a synchronous approach

“…Hence it is necessary to split the transitions across state boundaries. The solution is inspired from the translation of Esterel traps into SyncCharts, as proposed in Prochnow et al [37]. Figure 14 shows an example of such trap, emulated using immediate weak abortions: the traphalt signal may be emitted in order to prevent the termination at low-level if a trap with higher priority is emitted.…”

On the Pragmatics of Model-Based Design

“…Label placement is a big issue in graph drawing [21] and geography with map feature labeling [22]. The problem is computationally intensive, [25], converted from Esterel to Statecharts [26].…”

“…Having information in a textual representation can have many advantages [1,26]. There are already well accepted approaches for textual modeling available such as the Textual Concrete Syntax (TCS) [36] or Xtext [37], both frameworks for Eclipse.…”

Statechart Development Beyond WYSIWYG

“…The currently supported dialects are those of Esterel Studio, Stateflow, and the UML via the XMI format, as, e. g., generated by ArgoUML [18]. Alternatively, KIEL can synthesize graphical SSMs from (textual) Esterel v5 programs [6]. KIEL also provides an automated checking framework, which checks compliance to robustness rules [19].…”

“…There exist a couple of languages that either describe Statecharts directly (e. g., SCXML [3], SVM [4]) or indirectly (e. g., Esterel [5,6]). Consequently the developer of reactive systems may choose between the textual and the graphical approach to specify systems.…”