When a given system that depends on the fixed resources of b reaching the optimal solution of both objectives such as the best quality and the maximal profit purposes in the system, it is inappropriate to acquire external resources by any means in the real world for redesigning or reforming the optimized system, which would thereby break through the boundary of fixed resources.
Tzeng is based on variable space to realize the concept of ideal point (as shown in Figure 3-3), and proposes a new idea of multi-objective planning for decision space and target space.