Abstract
The purpose of this paper is to derive a general theory of design from experimental results of design by the method of structural analysis of them. A specification is given to designers. They discuss it, analyse it, propose tentative design solutions, and finally get to a conclusion which satisfies the specification. The conversation is recorded and reviewed to extract rules governing the thought process by which they converge to the conclusion. This experimental method is found useful to derive the general theory of design. Four models of designing process are extracted : (1) function-attribute transition model, (2) Markovian model, (3) flow diagram model, and (4) logical structure model. These represent characteristic aspects of designer's designing activity respectively. They reveal the merits and demerits of a designer, from which some proposals for improving the design efficiency are obtained, concerning the design process, such as sequence of design steps, amount of information given at each step, distribution of evaluation steps among others, etc. These proposals are useful for practical construction of CAD systems. The models are also compared with deductive models constructed by the axiomatic approach. Good correspondences are found between them.
