subject: A Look Into The History Of Design 2 [print this page] The Rational Model was independently developed by Simon and Pahl and Beitz. It posits that designers attempt to optimise a design candidate for known constraints and objectives, the design process is plan-driven, the design process is understood in terms of a discrete sequence of stages.
The Rational Model is based on a rationalist philosophy and underlies the Waterfall Model, Systems Development Life Cycle and much of the engineering design literature. According to the rationalist philosophy, design is informed by research and knowledge in a predictable and controlled manner. Technical rationality is at the centre of the process.
Typical stages consistent with The Rational Model include the following. Pre-production design, Design brief or Parti an early (often the beginning) statement of design goals, Analysis - analysis of current design goals, Research - investigating similar design solutions in the field or related topics, Specification - specifying requirements of a design solution for a product (product design specification) or service. Problem solving - conceptualizing and documenting design solutions, Presentation - presenting design solutions, Design during production, Development - continuation and improvement of a designed solution, Testing - in situ testing a designed solution, Post-production design feedback for future designs, Implementation - introducing the designed solution into the environment, Evaluation and conclusion - summary of process and results, including constructive criticism and suggestions for future improvements, Redesign - any or all stages in the design process repeated (with corrections made) at any time before, during, or after production.
The Rational Model has been widely criticized on two primary grounds. Designers do not work this way - extensive empirical evidence has demonstrated that designers do not act as the rational model suggests.
Unrealistic assumptions - goals are often unknown when a design project begins, and the requirements and constraints continue to change.
The Action-Centric Perspective is a label given to a collection of interrelated concepts, which are antithetical to The Rational Model. It posits that designers use creativity and emotion to generate design candidates, the design process is improvised, no universal sequence of stages is apparent - analysis, design and implementation are contemporary and inextricably linked.
The Action-Centric Perspective is a based on an empiricist philosophy and broadly consistent with the agile approach and a methodical development. Substantial empirical evidence supports the veracity of this perspective in describing the actions of real designers. Like the Rational Model, the Action-Centric model sees design as informed by research and knowledge. However, research and knowledge are brought into the design process through the judgment and common sense of designers - by designers thinking on their feet - more than through the predictable and controlled process stipulated by the Rational Model. Designers' context-dependent experience and professional judgment take centre stage more than technical rationality.
