Kurt Kohlstedt
99% Invisible
A Podcast by Roman Mars & Kurt KohlstedtInheriting Froebel's Gifts
A Podcast by Kurt KohlstedtFroebel’s Gifts were meant to be given in a particular order, growing more complex over time and teaching different lessons about shape, structure and perception along the way. A soft knitted ball could be given to a child just six weeks old, followed by a wooden ball and then a cube, illustrating similarities and differences in shapes and materials. Then kids would get a cylinder (which combines elements of both the ball and the cube) and it would blow their little minds. Some objects were pierced by strings or rods so kids could spin them and see how one shapes morphs into another when set into motion. Later came cubes made up of smaller cubes and other hybrids, showing children how parts relate to a whole through deconstruction and reassembly.
These perception-oriented “Gifts” would then give way to construction-oriented “Occupations.” Kids would be told to build things out of materials like paper, string, wire, or little sticks and peas that could be connected and stacked into structures.
The 99% Invisible City
A Book by Roman Mars & Kurt Kohlstedt
What's Wrong With This Model?
What's wrong with the rational model
- We Don’t Really Know the Goal When We Start
- We Usually Don’t Know the Decision Tree – We Discover It as We Go
- The Nodes Are Really Not Design Decisions, but Tentative Complete Designs
- The Goodness Function Cannot be Evaluated Incrementally
- The Desiderata and Their Weightings Keep Changing
- The Constraints Keep Changing
Deciding what to design
We Don’t Really Know the Goal When We Start
The most serious model shortcoming is that the designer often has a vague, incompletely specified goal, or primary objective. In such cases, the hardest part of design is deciding what to design.
I came to realize that the most useful service I was performing for my client was helping him decide what he really wanted.
Today, we recognize that rapid prototyping is an essential tool for formulating precise requirements. Not only is the design process iterative; the design-goal-setting process is itself iterative. Knowing complete product requirements up front is a quite rare exception, not the norm. Therefore, goal iteration must be considered an inherent part of the design process.
Evaluating goodness
The Goodness Function Cannot be Evaluated Incrementally
The Rational Model assumes that design involves a search of the decision tree, and that at every node, one can evaluate the goodness function of several downward branches. In fact, one cannot in general do this without exploring all the downward branches to all their leaves, which is possible in principle, but leads to a combinatorial explosion of alternatives in practice.
Changing constraints
The Constraints Keep Changing
The explicit listing of known constraints in the design program helps here. The designer can periodically scan the list, asking, “Can this constraint now be removed because the world has changed? Can it be entirely circumvented by working outside the design space?”
They just don't work that way
Perhaps the most devastating critique of the Rational Model, although perhaps the hardest to prove, is that most experienced designers just don’t work that way.
“Conventional wisdom about problem-solving seems often to be contradicted by the behavior of expert designers. Empirical studies of design activity have frequently found ‘intuitive’ features of design ability to be the most effective and relevant to the intrinsic nature of design. Some aspects of design theory, however, have tried to develop counter-intuitive models and prescriptions for design behavior.” — Nigel Cross
We must outgrow it
Why all this fuss about the process model? Does the model we and others use to think about our design process really affect our designing itself? I believe it does. I believe our inadequate model and following it slavishly lead to fat, cumbersome, over-features products and also to schedule, budget, and performance disasters.
The Rational Model, in any of its forms, leads us to demand up-front statements of design requirements. It leads us to believe that such can be formulated. It leads us to make contracts with one another on the basis of enshrined ignorance. A more realistic process model would make design work more efficient, obviating many arguments with clients and much rework.
The Waterfall Model is wrong and harmful; we must outgrow it.