Key challenges and opportunities in ´system of systems´ engineering

System of systems engineering (SoSE) extracts value from existing assets and designs new assets to be more easily re-purposed, than has been the case. One way SoSE arrives at a system of systems (SoS) is by interfacing or incorporating existing systems. Another way is by "harmonizing" a set of holons. Either way managing the on-going evolution of the SoS is more challenging than initializing the SoS. This paper presents the challenges and opportunities for the next generation of concepts, principles, methods and tools that are needed for creating and sustaining SoS\´s.