A Constraint-based Model of the Design Process
The fundamental goal of the engineering and industrial design disciplines is to conceive and implement the design, fabrication, and operation of objects to meet real human needs. When the process is successful, the outcomes are embodied in something tangible—an artifact, a system, or a process—that attempts to resolve some practical problem in a non–trivial way. ‘Non–trivial’ because these designed artifacts never exist in isolation: in order for a design to be successful it must adeptly balance the many contextual factors and constraints—from performance requirements and market trends to the activity and environment of use—that are intimately tied to a specific, and unique, design problem. What this paper proposes is that the complex and dynamic context within which all specific designs emerge is actually inherent within a larger constraint environment that shapes not only the artifact itself, but also its performance, operation, and evolution. We assert as well that the processes used to generate relevant knowledge and design concepts are also affected by this constraint environment. Here we propose a model of five distinct classes of constraints—physical, technical, market, socio-cultural, and usage—that give us a deeper understanding of this rich constraint environment and how it affects every aspect of design. By viewing all designs and their associated processes through this model we hope to provide a basis for explaining why, despite their fundamental similarity, the processes, methodologies, and outcomes associated with the engineering and industrial design disciplines are so different. While the different design disciplines all give some consideration to the major categories of constraints, the inescapable fact that designs are inherently resource–limited means that we can never exhaustively investigate all of the constraints present in any design. Additionally, while it is tempting to view design constraints as static, they are in reality co–evolving as a result of their interaction and competition with other constraints. As a result, the constraints on which each individual design discipline or process chooses to focus, as well as the way in which they dynamically balance these multiple constraints, largely defines the design space in which they work. We see constraints as fundamental to design and believe that in order to better understand how both designers and users understand and relate to a design at all stages of its life (research, design, usage, etc.), we must first focus on being able to identify and define constraints in a more rigorous way.