The Interaction Design Process

Instead the problem and the solution grow together. As you start to solve a problem you learn more about it and gain a deeper understanding of it. That in turn changes the solution, which again affects your understanding of the problem. This is a good thing.

Refusing to allow the problem to change over the course of the design means that you are tied in to your initial preconceptions - and those are frequently wrong. Sometimes dangerously so.

But if you allow the problem to adjust and grow as design proceeds you ensure that you end up with a product that genuinely solves the right problem.