Sometimes there’s a Heuristic That Almost Always Works, like “this technology won’t change everything” or “there won’t be a hurricane tomorrow”.
And sometimes the rare exceptions are so important to spot that we charge experts with the task. But the heuristics are so hard to beat that the experts themselves might be tempted to secretly rely on them, while publicly pretending to use more subtle forms of expertise.
…Maybe this is because the experts are stupid and lazy. Or maybe it’s social pressure: failure because you didn’t follow a well-known heuristic that even a rock can get right is more humiliating than failure because you didn’t predict a subtle phenomenon that nobody else predicted either. Or maybe it’s because false positives are more common (albeit less important) than false negatives, and so over any “reasonable” timescale the people who never give false positives look more accurate and get selected for.
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.