Frequently, complexity takes the form of a hierarchy, whereby a complex system is composed of interrelated subsyatems that have in turn their own subsystems, and so on, until some lowest level of elementary components is reached (Courtois, 1985). The choice of what components in a system are primitive is relatively arbitrary and is largely up to the discretion of the observer of the system. Intracomponent linkages are generally stronger than intercomponent linkages (components of a system are loosely coupled, but components themseklves are cohesive) (Simon, 1985). Hierarchical systems are usually composed of only a few different kinds of subsystems in various combinations and arrangements (same components can be reused)(Simon, 1985). A complex system that works is invariably found to have evolved from a simple system that worked..... A complex system designed from scratch never works and can not be patched up to make it work. You have to start over, beginning with a system that works (Gall, 1986).