Waterfall

Winston W. Royce’s 1970 paper, "Managing the Development of Large Software Systems," is often misrepresented as advocating pure Waterfall development — but he explicitly warned against strict all-upfront planning. Royce describes the classic sequential model — requirements → design → implementation → verification → maintenance — not to recommend it, but to critique it. He writes early in the paper:

"I believe in this concept, but the implementation described above is risky and invites failure."

In other words, he acknowledged the basic structure (phases are necessary) but said that rigid sequential execution is dangerous.

Managing the Development of Large Software Systems

FYI TBF