Evolution of production facilities and its impact on non-functional requirements

Due to high acquisition costs, production facilities are to operate for many years or even decades to be profitable. During operation, application and customer requirements change rather frequently. Therefore, a process operator must constantly evolve the control software and the underlying system. This task is restricted by specific constraints in the domain of production systems (e.g. short reaction times, high dependency on physics, etc.) hindering the proper use of formal engineering processes, which results in a lack of explicit documentation. Under such circumstances, it is evident that long-living automation software systems require special strategies to deal with incomplete information. Moreover, due to the complexity of production plants, the interconnection between evolution scenarios and system requirements might be complex. Then, a link between evolution and fulfillment of requirements is to be defined. In an effort to give a structured overview of the resulting difficulties due to improperly performed evolution steps in production facilities, this contribution presents a categorization of evolution scenarios from a practical point of view. In addition, interrelations between physical process measurements and high-level requirements are shown. This paper aims at describing the occurring difficulties within evolving production systems from a practical point of view and establishing a first step towards exploiting process measurements for requirement-aware production systems.