> So we're doing waterfall again?

The waterfall we know was always a mistake. The downhill only flow we know and (don't) love was from someone at DOD who only glanced at the second diagram (Figure 2) in the original 1970 Royce paper and said "This makes sense, we'll do it!" and... we're doing waterfall.

So, go to the paper that started it all, but was arguing against it:

- https://www.praxisframework.org/files/royce1970.pdf

I encourage you to look at the final diagram in the paper and see some still controversial yet familiar good ideas:

  - prototype first
  - coding informs design
  - design informs requirements
  - iterate based on tests -> design -> requirements (~TDD)

Crucially, these arrows go backwards.

See also the "Spiral Model" that attempts to illustrate this a different way: https://en.wikipedia.org/wiki/Spiral_model#/media/File:Spira...

Amazing that waterfall arguably spread from this paper, where it's actually an example of "what not to do."

Here's what Royce actually says about the waterfall diagram:

The implementation described above is risky and invites failure. … The testing phase which occurs at the end of the development cycle is the first event for which timing, storage, input/output transfers, etc., are experienced as distinguished from analyzed. These phenomena are not precisely analyzable. … Yet if these phenomena fail to satisfy the various external constraints, then invariably a major redesign is required. … The required design changes are likely to be so disruptive that the software requirements upon which the design is based and which provides the rationale for everything are violated. … One can expect up to a 100-percent overrun in schedule and/or costs.

This is 55 years ago.