Design Principles

Abstract

One way to look at software problems is with a model that divides the problems into two different layers:

• “Wicked” problems fall in the upper layer. These are problems that typically come from domains outside of computer science (e.g. biology, business, meteorology, sociology, political science, etc.). These types of problems tend to be open-ended, ill-defined, and large in the sense that they require much work. For example, pretty much any kind of a web commerce application is a wicked problem. Horst W. J. Rittel and Melvin M. Webber, in a 1973 paper on social policy,¹ gave a definition for and a set of characteristics used to recognize a wicked problem that we’ll look at later in this chapter.

• “Tame” problems fall in the lower layer. These problems tend to cut across other problem domains; they tend to be more well defined and small. Sorting and searching are great examples of tame problems. Small and well-defined don’t mean “easy” however. Tame problems can be very complicated and difficult to solve. It’s just that they are clearly defined and you know when you have a solution. These are the kinds of problems that provide computer scientists with foundations in terms of data structures and algorithms for the wicked problems we solve from other problem domains.

There are two ways of constructing a software design. One way is to make it so simple that there are obviously no deficiencies. And the other way is to make it so complicated that there are no obvious deficiencies. — C. A. R. Hoare