| The needs of computational tools provide the motivation to have a better understanding of the roles of knowledge and sketches in the design process. The inadequacies of current computer-aided conceptual design tools result from our vague comprehension of the nature of the design process. The hypothesis of this study is that the design process involves interlocked and multi-mode processes in which design knowledge and sketches interact with each other to advance the design process. These interactions make current computer-aided design systems unsatisfactory in the conceptual design process. The understanding of these interactions would provide the foundation of more useful computational tools and potentially play a role in developing better pedagogical methods. This research utilized both process-oriented and content-oriented coding schemes to examine different aspects of the design process. Concurrent and retrospective protocols were analyzed to determine their utility in revealing the design processes. Retrospective protocols and the content-oriented coding scheme were selected for design cognition studies in this research, and the procedures of experiments and analyses were described in detail. The results of encoded protocols were presented in terms of segments, levels, and instances. They represented the design process in a way that enabled us to observe the interactions among sketches, knowledge, and different cognitive levels. The examination of the conceptual design process demonstrated its features of interlinked levels and multiple modes; even one snippet of the process contained various modes and sub-processes. The shifting speed of intentions and the vagueness of sketches and functional references were also shown. The study of the meditated roles of the sketches and knowledge in the design process shows the following. First, sketches are the affordances of perceptual and functional instances while designing. Most of the sketches made by designers are multi-functionally bounded. Second, design knowledge plays various roles in the conceptual design process. The ubiquitous designerly way of knowing demonstrates the differences between active developing and passive utilizing design knowledge. Finally, one of the roles of design sketches and knowledge is shown to be the connector among different cognitive levels in the design process. The unpredictability of the design process is demonstrated in the results. Design knowledge provides previously generated solutions for the problem at hand, and design situatedness describes the phenomenon that a designer uses his/her experience to produce novelty and innovation. A method to measure the design innovation through an encoded protocol is proposed based on the concept of situated creativity. The implications for future computer-aided design systems are presented based on the roles of sketches, knowledge, and situatedness in the interlinked and multimode design process. The concept of cognition-oriented CAD is proposed to provide empirical clues to improve current CAD systems. |
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