[NB: This is an excerpt from https://pragprog.com/magazines/2013-02/estimation-is-evil, by Ron Jeffries. I've selected the vignette about C3 and piecewise updating because it applies to so many systems out there. The whole post is important, I hope you can read it all -- Peter]
One of the best-known long-term Agile projects was Chrysler’s C3 payroll, the first Extreme Programming project.
I was once present for an exchange between Sue Unger, then CIO of Chrysler Corporation, the highest-ranking IT executive I’ve ever met, meeting with the C3 team. Kent Beck had just explained how we’d be working in iterations of a few weeks duration, building whatever our “Customer,” Marie DeArment, asked us to build. Ms. Unger asked “How will I know whether you’re on track or not?”
Kent held up our stack of story cards for the payroll. “Here are all the things we have to do. We’ll be adding things as we discover them, and removing any that don’t need to be done. We ask you to visit us every month. We’ll show you these car