Caractérisation des systèmes autoguérissants : diagnostiquer ce que l’on va réparer Diagnose what you will repair : characterizing and checking self-healability

Modern systems, such as web services, need to be selfhealing, which means capable of surviving autonomously the occurrence of faults, still managing to provide the desired functionality. Designers of such systems need tools helping them to assess beforehands the self-healability of their system, but as a first step towards such tools, one needs to better define what self-healability precisely means in those applications. Diagnosability, which is the ability of a system to be self-aware about its current state by analysing the observations that are received, has been thoroughly defined, but it totally disregards repair capabilities. On the other hand, repairability considered as the ability of a system to react to faults by applying repair actions is useless if it disregards diagnosis. This paper goes further, defining self-healability as a joint property, which achieves a bridge between diagnosability, for which we had to extend the classical definition, and repairability, of which we provide a first formal definition ; we then propose a practical and tractable self-healability checking algorithm and suggest strategies to help designers building self-healing systems.