At one point or another in life, we all have been introduced to the waterfall project management way of working.
If you are one of the lucky ones that has never seen it, here is an image from the original white paper from Dr. Winston W. Royce.
So what is wrong with this way of working? Let us ask the author.
Right below the image, he writes. “I believe in this concept, but the implementation described above is risky and invites failure.”
For this methodology to work, one thing must be certain, the requirement will never change. EVER. Because otherwise, “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.”
We know the world is faster than ever and what today is true, tomorrow may be a lie. So it’s almost guarantee that requirements will change, and when they do “In effect the development process has returned to the origin and one can expect up to a 100-percent overrun in schedule and/or costs.”
Original paper : http://www-scf.usc.edu/~csci201/lectures/Lecture11/royce1970.pdf