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Waterfall Model
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The waterfall model is a sequential approach to software development in which requirements, design, implementation, testing and deployment proceed as separate phases, each completed before the next begins. The model is almost always traced to computer scientist Winston Royce's 1970 paper Managing the Development of Large Software Systems, but Royce's own paper argued against what industry practice later attributed to it: he called the single-pass version a simpler method, stated plainly that in my experience the simpler method has never worked on large software development efforts, and recommended iterative feedback loops between adjacent phases with major phases run twice. Later writers and practitioners cited Royce's paper, and especially its early illustrative diagram, in support of the rigid single-pass process he had explicitly warned against, one of the more consequential misreadings in software-engineering history, recorded as a dissent below. Whoever first used the word waterfall itself, the term became the standard name for the rigid process by the 1980s, commonly contrasted with the later iterative methods named agile.
Facts
Core PrincipleComplete each development phase, requirements, design, build, test, deploy, in strict sequence before the next phase begins, with no planned iteration back to an earlier phase. 1 Origin Year1970 is when Royce published the paper the model is traced to. The word waterfall itself is not Royce's own term, and its coining is not reliably dated to him or to this paper. Cross-Tradition Connections
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Dissenting Readings (1 dissenting reading)
Origin Year
Most software-engineering literature that cites Royce 1970 as the origin of the waterfall model gets his argument backwards. Royce called the strict single-pass sequence a simpler method and stated plainly that in his own experience it had never worked on large software efforts, recommending iterative feedback loops and doubled major phases instead. The paper became the standard citation for a rigid process its own author explicitly warned against, because later readers relied on its early illustrative diagram rather than the text that followed it.
A dissenting reading, from an independent laneDavid A. Wheeler, The Waterfall Model (David A. Wheeler)
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