Section: New Results

CCSL as a Logical Clock Calculus Algebra: expressiveness and analysis techniques

Participants : Robert de Simone, Julien Deantoni, Frédéric Mallet, Dongdong An.

CCSL is a simple, half-declarative and half-imperative language describing relations and constraints between sequences of events considered as Logical Clocks. The usage of CCSL for specification of embedded systems is powerful in that it defers the precise setting of physical timing until later implementation design phases (which may vary according to circumstances), see 3.2.

Early this year we established the universal recursive expressivity of CCSL, by encoding the dynamics of Petri Nets with inhibitor arcs in our framework (still unpublished). Those results were presented by Robert de Simone in a keynote talk at Memocode 2016. This result prompts the use of non-automatic methods for establishing actual schedules as solutions of CCSL specifications seen as schedulability constraints. Steps in that direction were made in [37].

We also considered the extension of CCSL towards stochastic modeling of potential input clocks as my emerge from the Cyber-Physical world (mixing probabilistic modeling of external events with discrete transformations by discrete cyber digital controlers). This work was initiated in [28], and should be further extended in the ongoing PhD thesis of Dongdong An.

Finally, we have also investigated to decide on specific schedules (e.g. periodic schedules) valid for a subset of CCSL. We have established a sufficient static condition for the existence of such a periodic schedule as well as a practical implementation to build such a solution [39] based on a SMT solver.