A number of experts in the sphere of planning have distinguished between three different models of planning:

It should be mentioned that they are useful as conceptual tools to highlight different aspects of planning, but not as models existing in pure forms. In practice these models are inevitably combined.

Comprehensive rational planning can be presented by a continuous circle (Fig. 1), including:

The cycle starts again with the reassessment or evaluation of the situation.

Figure 1. Comprehensive rationalism planning circle (E. Green "An Introduction to Health Planning in Developing Countries")

Comprehensive rationalism is a planning model based on a complete analysis of every possible alternative. This model of planning has its advantages and disadvantages. .

Advantage:

• all possible courses of action (including the "best one") are considered

Disadvantages:

• Conditions (for complete analysis) cannot be met - in real life it is impossible to carry out such a comprehensive and exhaustive list of operations. The information and human- resource requirements of examining the detailed implication of each option are vast.
• Approach suggests a chronologically ordered cycle of events each starting from the previous one. In practice a number of sub-cycles are likely to be set. Indeed, various activities may occur in parallel.