Design Prototypes

This article commences with an elaboration of models of design as a process. It then introduces and describes a knowledge representation schema for design called design prototypes. This schema supports the initiation and continuation of the act of designing. Design prototypes are shown to provide a suitable framework to distinguish routine, innovative and creative design. DESIGN Although there are designers who claim design is a mysterious activity not amenable to scientific examination, there continues to be research into design. Although there are publications by designers on how to design dating back to Roman times, notably by Vitruvius, the nineteenth century design thinkers commenced work on articulating design as a process (Durand, 1802). However, it was not until the 1960s that major research programs were initiated. These were originally founded on the systems view and utilised concepts from operations research (Jones and Thornley, 1963). More recently, information processing models founded on artificial intelligence concepts have provided an impetus for renewed research into design in its various aspects (Simon, 1969; Coyne et al., 1990). Many foundational ideas in artificial intelligence are proving to be useful in developing formal models of design as an activity. WHAT IS DESIGN Designers are change agents in society. Their goal is to improve the human condition, in all its aspects, through physical change. Although design for many continues to remain a mysterious activity, it has been recognized as an important activity for more than 4,000 years. Approximately 2,000 BC, Hammurabi, King of Babylon, enacted a law which both recognized design and made it dangerous, figure 1. Design research has a number of goals including: gaining a better understanding of design, developing tools to aid human designers, and the potential automation of some design tasks. Figure 1. Hammurabi's Code, from an engraving on a stella in cuneiform in the Louvre, Paris. "If a designer/builder has designed/built a house for a man and his work is not good, and if the house he has designed/built falls in and kills the householder, that designer/builder shall be slain." Design appears to be carried out differently to the way we are taught to understand the world, which is largely derived from the Greek view of the world. Science has been developed as a means of attempting to explain and understand the world around us. It commences with a description of the world (which in itself is not a trivial act to produce) and some behaviors and attempts to produce causal dependencies between them. Science then may be used to attempt to produce a purpose for the world. Design exists because the world around us does not suit us and the goal of designers is to change the world through the creation of artefacts. They do this by positing functions to be achieved and producing descriptions of artefacts capable of generating those functions. In this sense, design is the opposite of the traditional scientific explanation. Thus, design is purposeful and the activity of designing is goal-oriented. The meta-goal of design is to transform requirements, more generally termed functions which embody the expectations of the purposes of the resulting artefact, into design descriptions. The result of the activity of designing is a design description. This design description generally is represented graphically, numerically, and/or textually. The purpose of such a description is to transfer sufficient information about the designed artefact so that it can be manufactured, fabricated or constructed. A prevalent and pervasive view of designing is that it can be modeled using variables and decisions taken about what values should be taken by those variables. The activity of designing is carried out with the expectation that the designed artefact will operate in the natural world and the social world. These impose constraints on the variables and their values. So design could be described as a goal-oriented, constrained decision-making activity. However, design distinguishes itself from other similarly described activities not only by its domain but equally importantly by additional necessary features. Designing involves exploration: exploring what variables may be appropriate. The process of exploration involves both goal variables and decision variables. In addition, designing involves learning: part of the exploration activity is learning; learning about emerging features as a design proceeds. Finally, design activity occurs within two contexts: the context within which the designer operates and the context produced by the developing design itself. The designer's perception of what is the context affects the implication of the context on the design. The context shifts as the designer's perceptions change. Design activity can be now characterized as: a goal-oriented, constrained, decision-making, exploration and learning activity which operates within a context which depends on the designer's perception of the context. MODELS OF DESIGN The purpose of designing is to transform function, F (where F is a set), into a design description, D, in such a way that the artefact being described is capable of producing those functions. For example, when designing windows some of the functions include the provision of daylight, control of ventilation and the provision of access to a view. The design description would take the form of drawings and notes. Thus, a naive model of design is F -> D where -> is some transformation. There is, however, no direct transformation capable of achieving this result. A design description represents the artefact's elements and their relationships, this is labelled structure, S. In the window design example the artefact's elements are the glazing and the frame and their topology. Computer-aided drafting systems have become the means by which structure is transformed into a design description, i.e.