Section: New Results

Logical Time for Safety Analysis and dependability

Participants : Paul Bouche, Amin Oueslati, Robert de Simone.

We have studied in the past the relevance of Logical Time for modeling of dynamic Non-Functional Properties (NFP) aspects of functional applications and/or execution platforms. In this setting, any recurring events may be seen as generating its own “rythm”, as a logical clock. The most obvious NFP aspects to consider were performance and power consumption, as important concerns of Real-Time Embedded systems. Recently we have turned towards fault tolerance and availability/dependability aspects. This was motivated by demands from industrial partners inside IRT Saint-Exupery, who tried to design in real terms the digital computing structure of micro-satellites using ordinary processor components from the Shelf (COTS), extremely sensible to solar radiations (creatings faults). We have put up a full model-based design of the proposed use case, which includes modeling of the fault-tolerant features, but also the independent modeling of waterfall propagation schemes from incidental faults to fully recognized dysfunctions, where the system is no longer operational. Current results are encouraging, as they build up natural specification styles using logical time on top of existing formalisms such as AltaRica, widely used in industry. Methodological advances are proposed to industrial partners in IRT Saint-Exupery, and primarily Thales Alenia Space. We plan to comfort our approach next year with dedicated tools for modeling and analysis, as well as translation towards existing formalisms such as AltaRica, seen as lower level in our context.