Planning models

At present, the term planning has many meanings and little substance. It is an omnibus word or a dressing gown under which a variety of management matters masquerade. So many management activities are described as planning that the significance of the term may have succumbed to generality. The planning function appears to be a status generator, presumably because planning is closely associated with top managements' interests. It is surrounded with emotional issues furthermore, that help to obscure the difference between what we say we are doing (i.e., planning) and what we are doing (?). Although planning models are the subject of this paper, from the viewpoint of consistent terminology and unambiguous definition they don't exist. On the other hand, as judged by common usage, most management science models qualify as planning models. At the uppermost entrepreneurial levels planning is almost exclusively an intuitional affair. But characteristically these domains are dramatically unstable. No maps exist for traveling in such regions. Usually, even the fundamental dimensions are unknown. What planning models have been built to cope with these real and vital top-management problems? Search and survey answers, none. Consequently, a paper about planning models can either continue as in present practice to ignore critical issues, or can begin with simple classification-more or less as Linnaeus started back in the 1700's. We have chosen the latter course and begin this paper by attempting to develop a workable taxonomy. First, a relatively rigorous system for distinguishing between planning models and other kinds of models is provided. Then, the attempt is made to differentiate between three types of planning models... as shown in the abbreviated outline below: I. Broad definition of the planning function is given in terms of unit decisions-used as basic building blocks. II. Plans are contrasted with policies and this dichotomization of management activity becomes a basis for the formal definition of planning. III. Three types of planning models are defined. A. Fully-constrained planning systems-typically, PERT-type models which are more compelling as technological descriptions of the attributes of a system than for their methodological strengths. Fully-constrained systems are determinate requiring consideration of only a single path. B. Partially-constrained planning systems-are conceptually much closer to reality and are accordingly more complex. Adequate methodology is relatively non-existent. Partially-constrained systems, being stochastic, require consideration of alternative paths. Although amenable to statistical analysis, present interest has focussed on simulation using heuristic procedures. This is less in the sense of traditional science than in that of sculpture and architecture. C. Threshold-constrained planning systems-are associated with systems having high levels of vulnerability to ruin. These models are a special class of partially-constrained planning systems and so they also involve consideration of alternative paths. They span so-called master-planning and long-range planning activities where the state of the art can be characterized as "somewhere between the Ptolemaic and Copernican systems."