Graphical models for the assessment of safety and risk analysis of systems in the presence of uncertainties.

Summary Systems of Systems (SoS) are large systems whose components are themselves systems that interact to perform certain functions, and for which the malfunction of a single system can have serious consequences on the operation of the entire SoS. It is therefore important that the design of these SoSs takes into account the requirements of Dependability and in particular their reliability and availability when they are solicited. Moreover, it is necessary that it ensures, through quantitative analysis, that these requirements are met. Uncertainty is also an important part of the thesis, because there are always differences between a system and its representation by a model. The objective of this thesis is to propose a methodology for the safe design of SoSs. The first step is to propose a dysfunctional model of the global SoS integrating the hardware aspects, the network aspects and the human factor. In a second step, we evaluate the SoS requirements. In a third step, it is about taking into account different types of uncertainties in the models. Concerning the application part, the subject would be articulated around the safe design of a railway system. The main contribution of this thesis lies in three aspects. First, a general methodology for modeling SoSs is proposed. Second, we consider ERTMS Level 2 as a SoS and evaluate its SoF requirements taking into account the unavailability of the SoS as an emergent property. Third, different types of uncertainties are quantitatively modeled in the proposed models using probabilistic and non-probabilistic theories.