Waterfall model

The waterfall model is a software development model first proposed in 1970 by W. W. Royce, in which development proceeds linearly through the phases of requirements analysis, design, implementation, testing (validation), integration and maintenance.

In practice, the process rarely proceeds in a purely linear fashion. Iterations, by going back to or adapting results of the precedent stage, are common. The Waterfall model is considered old-fashioned or simplistic by proponents of object-oriented design which often uses the spiral model instead.

In the original article, Royce advocated using the model repeatedly, in a iterative way. However, most people do not know that.

This article (or an earlier version of it) contains material from FOLDOC's article on Waterfall Model, used with permission.