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Two examples of plant design are described and an abstract model of the process of design is suggested. The model is used to discuss the search for possible solutions, the strategies for their examination, and the rules for choosing between them. It seems likely that the model applies only to problems requiring novel solutions and not to those for which the form of solution is known, but the choice of parameters to meet conflicting objectives is difficult.
D. L. Marples (Thu,) studied this question.