Modules and Wholes

My koan (riddle) for today is how to design for the unknown. I can't seem to nail down what the user requirements are. Asking other people what they need doesn't bring any more clarity. I don't have the luxury to try out different alternatives, and test them. No, I simply have to make an poorly informed guess about what users need, and live with it. I am unfamiliar enough with the subject domain that I have learned not to trust my instincts -- they aren't a reliable indicator of what is required. A very frustrating situation to be in, though a common one, especially where new product or process in involved.