Understanding the Safety Lifecycle of Systems of Systems

The term Systems of Systems has increasingly been used to describe classes of systems exhibiting a combination of characteristics such as emergence, autonomy and independent development of their constituent systems. Safety is a system property, the achievement of which has a crucial influence on the system’s final acceptance. Due to its importance, safety should be methodically analysed along the system lifecycle. A number of standards and recommended practices define the processes and the objectives of the safety lifecycle, such as the ARP 4761. However the artefacts produced during the development of an SoS differ from ‘traditional’ development. The (UK) Ministry of Defence Architectural Framework (MODAF) – the UK equivalent of DODAF – is a prominent framework used in the defence domain. MODAF is organised in views, each of which focuses on a single aspect of the system operation. The Activity Based Methodology (ABM) has been proposed to structure the products MODAF. The paper presents how the traditional safety lifecycle can be adapted in presence of the artefacts used in SoS development. Moreover the paper discusses the MODAF products more suitable to reveal SoS issues affecting safety. Finally the paper discusses a number of issues that may challenge the application of the proposed lifecycle.