Substantial disagreement exists concerning how designers in many fields, whether amateur or professional, alone or in teams, produce designs. Design researchers Dorst and Dijkhuis acknowledged that "there are many ways of describing design processes," and compare and contrast two dominant but different views of the design process: as a rational problem-solving process and as a process of reflection-in-action. They suggested that these two
paradigms "represent two fundamentally different ways of looking at the world
positivism and
constructionism." The paradigms may reflect differing views of how designing
should be done and how it
actually is done, and both have a variety of names. The problem-solving view has been called "the rational model," an American scientist, and two German engineering design theorists, Gerhard Pahl and Wolfgang Beitz. It posits that: • Designers attempt to
optimize 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 According to the rationalist philosophy, design is informed by research and knowledge in a predictable and controlled manner. Typical stages consistent with the rational model include the following: • Pre-production design •
Design brief – initial statement of intended outcome. •
Analysis – analysis of design goals. • Research – investigating similar designs in the field or related topics. •
Specification – specifying requirements of a design for a product (
product design specification) or service. •
Problem solving –
conceptualizing and
documenting designs. •
Presentation – presenting designs. • Design during production. •
Development – continuation and improvement of a design. •
Product testing –
in situ testing of a design. • Post-production design feedback for future designs. •
Implementation – introducing the design 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. Each stage has many associated
best practices.
Criticism of the rational model 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.
Action-centric model The action-centric perspective is a label given to a collection of interrelated concepts, which are antithetical to the rational model. At least two views of design activity are consistent with the action-centric perspective. Both involve these three basic activities: • In the
reflection-in-action paradigm, designers alternate between "
framing", "making moves", and "evaluating moves". "Framing" refers to conceptualizing the problem, i.e., defining goals and objectives. A "move" is a tentative design decision. The evaluation process may lead to further moves in the design. which may start with the thinking of an idea, then expressing it by the use of visual or verbal means of communication (design tools), the sharing and perceiving of the expressed idea, and finally starting a new cycle with the critical rethinking of the perceived idea. Anderson points out that this concept emphasizes the importance of the means of expression, which at the same time are means of perception of any design ideas. == Philosophies ==