Since decades, the vital functions of the plant management are handled by automation systems of measurement, protection, control, monitoring and supervision, made with programmable electronic technologies. These systems are typically distributed within the plants, and are interconnected by communication networks by means of local and remote connections which, in many cases (e.g. electrical system) can extend on very long distances. In this framework plants depend more and more on the reliability and functionality of their communication infrastructure and of their automation systems and subsystems. If some of the functions involve safety issues, the reliability of the systems that perform these functions must be strongly validated and must grant adequate safety levels. In other words it is necessary to manage the so-called functional safety of the system or subsystem in accordance to the "life cycle approach".
Functional safety is defined as the part of the overall safety of the equipment or process and control systems associated with them which depends on the correct functioning of the electrical, electronic and programmable electronic safety-related applications or other technological systems for safety applications.