The hierarchy of systems and subsystems included in a total-ship-system is rightly called a "super system" (Hockberger, 1996). At the bottom of this hierarchy are the detailed components and characteristics that define the ship. Many lower-level system decisions can be made at their own level or one higher. Others must be determined at the total ship level. Some compromise between global and local optimization is essential to keep the problem manageable. The number of DPs at any level must be kept to the minimum necessary to capture important interdependence. The highest level of optimization should consider only those variables that have a major impact on ship balance. Frequently combat systems, HM&E systems and ship characteristics can be grouped into synergistic packages or suites. This reduces the number of variables that must be managed early in the design process.