Large systems that are formed from a variety of component systems: custom systems, which are newly engineered from the “ground up;” existing commercial-off-the-shelf (COTS) systems that are subsequently tailored for a particular application; and existing or legacy systems. Such related terms as systems of systems (SOS), federations of systems (FOS), federated systems of systems (F-SOS), and coalitions of systems (COS) are often used to characterize these systems. These appellations capture important realities brought about by the fact that modern systems are not monolithic. Rather, they have five characteristics, initially summarized by Mark Maier, that make one of the system family designations appropriate: