Optimization denotes the selection of a "best" decision out of a set of "feasible" decisions. What exactly a "best" and a "feasible" decision is, has to be defined formally in a mathematical manner by functions and relations. Such a definition specifies a mathematical optimization problem, in which the optimality of solutions is rigorously defined and is no longer a matter of opinion. In reality, still such a model-optimal solution need not be what the user wants. This, in contrast, usually is a matter of opinion. In the case of dissent, the model has to be revised until model-optimal solutions fit the users' needs.