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 to be discredited for use as a Real World process by many modern software engineers, who are often proponents of agile processes instead.

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

See also: Project lifecycle, Spiral model, Chaos model.

External Link:

• Discussion on c2.com