This is it, I distinctly recall a reading a paper defining Waterfall as a thought exercise, with the author coming back years later to clarify that there can ne

This is it, I distinctly recall a reading a paper defining Waterfall as a thought exercise, with the author coming back years later to clarify that there can never be such a thing in software development. The Wikipedia article for "Waterfall model" mentions something like that as well. As an old teacher used to say, "There's no such thing as a Waterfall model, it was your parents all along. All software development is iterative."