Online evaluation of resilience
Usually, dependability assessment is carried out only once during system design, in order to define an appropriate system architecture, satisfying the system dependability requirements. When in operation, the success of a mission is subject to the fulfillment of specific operational requirements that should be satisfied even in the presence of faults. Indeed, during a mission, the effects of some failures can be very severe if they are not anticipated. Using dependability assessment during system operation could be very helpful to anticipate and avoid system failure (or mission interruption). To this end, we have developed a modeling approach, based on a meta-model used to i) structure the information needed to assess operational reliability and to ii) build a stochastic model to be tuned dynamically to take into account the system operational state, the mission profile and the maintenance facilities . This model allows to i) assess, on-the-fly, the ability to succeed in continuing on the remaining part of the mission, in case of an unscheduled event occurrence, and to ii) support maintenance planning. The main difficulties come from the fact that the model is to be tuned, in operation, by operators who are not expert in dependability modeling techniques. Hence the model should be structured in a way that makes it easily and very quickly configurable in operation. It is built and validated off-line by modeling specialists, and can be tuned during operation by non-specialists. The approach has been illustrated on case studies related to aircraft subsystem, in collaboration with AIRBUS. The models are built based on the Stochastic Activity Networks formalism. The results show how to re-schedule a mission, based on the nature of the component in failure and its impact on the remaining part of the mission, as well as the maintenance possibilities at the various stops of the aircraft .
 K. Tiassou, K. Kanoun, M. Kaâniche, C. Seguin, C. Papadopoulos, "Aircraft Operational Reliability - A Model-Based Approach and a Case Study", Reliability Engineering & System Safety, vol. 120, décembre 2013, pp. 163-176.
 K. Tiassou, K. Kanoun, M. Kaâniche, C. Seguin, C. Papadopoulos, "Impact of Operational Reliability Re-assessment during Aircraft Missions", 31st IEEE International Symposium on Reliable and Distributed Systems (SRDS 2012), Irvine, CA, USA, 8-11 octobre 2012, pp.219-224.