Solution procedures can be either single pass or iterative. A single-pass solution procedure is one in which the final values of all the decision variables are determined simultaneously according to some well-defined procedure. An iterative solution technique, on the other hand, is one in which a number of steps are required to arrive at a final solution and where partial or complete solutions are entertained at each step. Discrete or continuous variables are frequently necessary for a particular problem. Finally, an optimal is one that can be shown to be at least as good as any other given the assumptions of the model, whereas a satisfactory solution is one that is considered "good" with respect to the objectives and constraints, yet cannot be shown to be the best. Thus, if in our previous example of the normative-static-deterministic model the decision variables are continuous, the relationships linear, and an optimal solution is desired, the list of potential solution techniques for the model can be reduced to just one-linear programming. In this way, one or more viable alternatives for the solution methodology can be identified, and the formulation of the model can begin.