Section: New Results

Components and contracts

Participants : Alain Girault, Christophe Prévot, Sophie Quinton, Jean-Bernard Stefani.

Contracts for the negotiation of embedded software updates

We address the issue of change during design and after deployment in safety-critical embedded system applications, in collaboration with Thales and also in the context of the CCC project (http://ccc-project.org/).

In collaboration with Thales, we mostly focus on timing aspects with the objective to anticipate, at design time, future software evolutions and identify potential schedulability bottlenecks. This year we have paved the way for an extension, to more complex systems, of the approach developed last year to quantify the flexibility of a system with respect to timing. Specifically, we have focused on systems with task chains, and have proposed new methods for computing upper and lower bounds on task chain latencies. This work will be submitted to a conference early 2018. Our methods are also being implemented in the Thales tool chain, in order to be used in industry.

Location graphs

The design of configurable systems can be streamlined and made more systematic by adopting a component-based structure, as demonstrated with the Fractal component model  [38]. However, the formal foundations for configurable component-based systems, featuring higher-order capabilities where components can be dynamically instantiated and passivated, and non-hierarchical structures where components can be contained in different composites at the same time, are still an open topic. We have recently introduced the location graph model [70], where components are understood as graphs of locations hosting higher-order processes, and where component structures can be arbitrary graphs.

We have continued the development of location graphs, revisiting the underlying structural model (hypergraphs instead of graphs), and simplifying its operational semantics while preserving the model expressivity. Towards the development of a behavioral theory of location graphs, we have defined different notions of bisimilarity for location graphs and shown them to be congruences, although a fully fledged co-inductive characterization of contextual equivalence for location graphs is still in the works. This work has not yet been published.