CYBER-PHYSICAL SYSTEMS (CPS): THE "SYSTEMS-OF-SYSTEMS" CHALLENGES

The ubiquitous deployment of software-based systems demands increased dependability of these systems, including safety, reliability, availability, security, maintainability, survivability, etc. The design, operation, and protection of these systems have to take into account the complex interplay of software, hardware, networks, environment and humans acting in different roles, including unexpected, emergent system behaviour and unexpected behaviour or threats experienced from the real-world environment. An additional dimension is added by the fact that we have not only to look at simple independent systems but on interlinked system(s) of systems, composed of (legacy) systems originally designed as independent systems), which interact in a much more complex manner, where it becomes much more difficult to separate different concerns regarding dependability properties. The interplay between humans, environment and systems must be considered in a holistic, interdisciplinary view for the distribution of tasks, mutual overriding mechanisms for decisions by humans, for performing interventions at system failures, etc. Systems must be robust to cope with these problems in an adaptive manner ("resilient systems), which is an ever increasing challenge for system design, verification, validation and deployment. Each of the "system of systems" has to follow its own strategy to avoid dangerous (critical) interactions respectively to tolerate them in an acceptable manner (risk reduction). Typical examples are critical infrastructures and their resilience requirements and protection, becoming interconnected and interdependent in a global context. "Cyber-physical Systems" is a new term recently arising to describe the notion of "embedded systems" as a network of interacting elements within the physical world, comprising an intense link between the computational and physical elements. Resilience is the persistence of service delivery that can justifiably be trusted when facing changes, i.e., the persistence of dependability when facing changes. Resilient embedded systems are the next challenge - adding new dimensions of complexity to manage!