DERIVING TRACTABLE SUB-SYSTEM FOR MODEL OF LARGER SYSTEM

The invention concerns reduction of a complex model of a system to a simpler model. The invention defines a task postulates a simple sub-system, and inquires whether the sub-system achieves the task. If not, the invention selects components from the complex model, based on functional relationship of the components to the task, adds the components to the simpler sub-system, and again inquires whether the sub-system achieves the task. The addition process is repeated until a sub-system is attained which does achieve the task.