Requirements engineering for complex systems

Abstract

Requirements Engineering (RE) is a part of Software Engineering and, in general, of System Engineering. RE aims to help in building software which satis es the user needs, eliciting, documenting, validating and maintaining the requirements that a software has to adequately satisfy. During its 30 years of RE history, its importance has been perceived with various degrees, from being the most important activity, well formalized and de ned in big complete documents which were the bible of the software project, to the opposite side where it has been reduced to just an informal activity, volatile, never formalized, not at all maintained, because ever changing. The need for well managing requirements is extremely important, mainly for complex systems which involve great investments of resources and/or cannot be easily substituted. A system can be complex because it is realized by the collaboration of a numerous and heterogeneous set of stakeholders, as for example in a big industrial research project, often co-funded with public resources, where usually many partners, with di erent backgrounds and languages must cooperate for reaching the project goals. Furthermore, a system can be complex because it constitutes the IT system of an Enterprise, which has been grown, along the time, by adding many pieces of software, integrated in many and di erent ways; the IT system is often distributed, ubiquitously interoperates on many computers, and behaves as a whole big system, though developed by many software providers, at di erent times, with di erent technologies and tools. The complexity of these systems is highly considered for several critical industrial domains where features of real-time and fault-tolerance are vital, such as automotive, railway, avionics, satellite, health care and energy; in these domains a great variety of systems are usually designed and developed by organizing and integrating existing components that pool their resources and capabilities to create a new system which is able to o er more functionalities and performances than those o ered by the simple sum of its components. Typically, the design and management of such systems, best known as System of Systems (SoS), have properties not immediately de ned, derived and easily analyzed starting from the properties of their stand-alone parts. For these reasons, SoS requires suitably engineered methods, tools and techniques, for managing requirements and any other construction process phase, with the aim to minimize whichever risk of fail. However, every complex IT system, even though it does not deal with a critical domain, but it supports the core business of an enterprise, must be well governed to avoid the risk of becoming rapidly inadequate to its role. This risk becomes high when many uncontrolled IT developments, aimed at supporting requirements changes, accumulate. In fact, as the complexity grows up, the IT system might become too expensive to maintain and then it should be retired and substituted after some too short time, often with big and underestimated di culties. For these reasons, complex systems must be governed during their evolution, both from the point of view of 'which application is where and why', and from the point of view of the supported requirements, that is 'which need is supported by each application and for whom'. This governance would facilitate the knowledge, the management, the essentialness and the maintenance of the complex systems, by allowing e cient support and a long-lasting system, with the consequence of minimizing waste of costs and inadequacy of the support for core business of the enterprise. This work addresses mainly the issue of governing systems which are complex because either they are the result of the collaboration of many di erent stakeholders (e.g. are big co-funded R&D projects) or they are Enterprise Information Systems (EIS) (e.g. IT system of medium/large enterprises). In this direction, a new goal-oriented requirements methodology, named GOReM, was de ned which has speci c features useful for the addressed issues. In addition a new approach, ResDevOps, has been conceived, that allows to re ne the government of the requirements of an EIS which is continuously improved, and which increases and evolves along the time. The thesis presents the framework of state of the art in which these activities found their collocation, together with a set of case studies which were developed inside some real projects, mainly big projects of R&D which have seen involved the University of Calabria, but also some cases in real industrial projects. The main results were published and were included in international conference proceedings and a manuscript is in press on an international journal.