Walk Appeal promises to be a major new tool for understanding and building walkable places, and it explains several things that were heretofore either contradictory or mysterious. It begins with the assertion that the quarter-mile radius (or 5-minute walk,) which has been held up for a century as the distance Americans will walk before driving, is actually a myth.
Both images below are at the same scale, and the yellow dashed line is a quarter-mile radius. On the left is a power center. As we all know, if you're at Best Buy and need to pick something up at Old Navy, there's no way you're walking from one store to another. Instead, you get in your car and drive as close as possible to the Old Navy front door. You'll even wait for a parking space to open up instead of driving to an open space just a few spaces away… not because you're lazy, but because it's such a terrible walking experience.
The image on the right is Rome. The circles are centered on the Piazza del Popolo (North is to the left) and the Green radius goes through the Vittorio Emanuele on the right. People regularly walk that far and then keep on walking without ever thinking of driving.
While the client has some knowledge of his symptoms, he may not understand the real causes of them, and it is foolish to try to cure the symptoms only. Thus while the systems engineers must listen to the client, they should also try to extract from the client a deeper understanding of the phenomena. Therefore, part of the job of a systems engineer is to define, in a deeper sense, what the problem is and to pass from the symptoms to the causes.
Just as there is no definite system within which the solution is to be found, and the boundaries of the problem are elastic and tend to expand with each round of solution, so too there is often no final solution, yet each cycle of input and solution is worth the effort. A solution which does not prepare for the next round with some increased insight is hardly a solution at all.
I suppose the heart of systems engineering is the acceptance that there is neither a definite fixed problem nor a final solution, rather evolution is the natural state of affairs. This is, of course, not what you learn in school, where you are given definite problems which have definite solutions.