The Role of Parts in the System Behaviour

In today’s world, we are surrounded by software-based systems that control so many critical activities. Every few years we experiment dramatic software failures and this asks for software that gives evidence of resilience and continuity. Moreover, we are observing an unavoidable shift from stand-alone systems to systems of systems, to ecosystems, to cyber-physical systems and in general to systems that are composed of various independent parts that collaborate and cooperate to realise the desired goal.Our thesis is that the resilience of such systems should be constructed compositionally and incrementally out of the resilience of system parts. Understanding the role of parts in the system behaviour will (i) promote a “divide-and-conquer strategy” on the verification of systems, (ii) enable the verification of systems that continuously evolve during their life-time, (iii) allow the detection and isolation of faults, and (iv) facilitate the definition of suitable reaction strategies. In this paper we propose a methodology that integrates needs of flexibility and agility with needs of resilience. We instantiate the methodology in the domain of a swarm of autonomous quadrotors that cooperate in order to achieve a given goal.