A non-dominated solution, for a given problem and constraints, is a feasible solution for which no other feasible solution exists which is better in one objective attribute and at least as good in all others. Figure 1 illustrates this concept for a simple two objective (cost-effectiveness) problem. The heavy curve represents non-dominated solutions or the Pareto-optimal frontier. The preferred design should always be one of these non-dominated solutions. Its selection depends on the decision-maker’s preference for cost and effectiveness. This preference may be affected by the shape of the frontier and cannot be rationally determined a priori.