A discussion of Winston W. Royce's 1970 paper “Managing the Development of Large Software Systems 
.” It's an influential paper that went horribly wrong. Why?
(For a linear treatment (audio with transcript) see Oops! The Winston W. Royce story .)
I blame metaphor and the perverse affordances of diagrams.
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Royce70's Description of Waterfall (The name had not been invented yet.)
Royce70 and Rework: Royce thinks small iterations to fix errors made in the previous phase are "scoped down to manageable limits." His concern is errors that ripple back to require rework in much earlier phases, rework that then ripples forward – at great cost.
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The Waterfall Metaphor as Metaphor leads people to assume (at a semi-conscious level) that software development can and *ought to be* akin to the natural flow of water downhill. Well, it's not. Fish Ladder Analogy
Royce70 Metaphor Advice gives two heuristics.
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Royce70's Diagrams inflate the appeal of waterfall and reduce the appeal (and memorability) of his solution.
Royce70 Diagram Advice gives heuristics.