A
software life-cycle or
product life-cycle
model, described by W. W. Royce in 1970, in which development
is supposed to proceed linearly through the phases of
requirements analysis, design, implementation, testing
(validation), integration and maintenance. The Waterfall
Model is considered old-fashioned or simplistic by proponents
of
object-oriented design which often uses the
spiral model instead.
Earlier phases are sometimes called "upstream" and later ones
"downstream".
Compare: iterative model.
[W. W. Royce, "Managing the Development of Large Software
Systems", Proceedings of IEEE WESCON, August 1970].