Towards a discipline of system engineering: validation of dependable systems

Complex systems require the use of an integrated and best balanced set of components. The integration and the balanced set are crucial issues, which require some sort of verifiable compositionality property of component parts that contribute structurally, functionally, non functionally and interactionally to the total quality of the system design. This is even more important when dealing with the design of highly dependable systems. The concept of verifiable compositionality is much more demanding than the usual approach based on composition of building blocks. It implies the presentation of properties and the ability of verifying them, as well as those that are added (which mainly deal with interactions among parts) in the process of designing and building a system made of components. Economic reasons push towards the use of COTS (Commercial Off the Shell) and towards the re-use of available components and this trend poses new problems. Integration, compositionality and re-use appear to be tile very challenging issues in the validation (of both design and implementation) of complex systems, in particular dependable ones used for controlling critical applications, and require a special effort towards the emergence of a new discipline-System Engineering-which will encompass and integrate the current design disciplines. This paper aims at a discussion in the direction of identifying possible advanced approaches to the validation of dependable systems.