[irrational]

But waterfall or agile implies code is being written. My take on this (and experience) is that sometimes you just takes weeks, months, even years to just make notes in a notebook, ponder and think upon the problem, jot down more notes, look around at other peoples code, do research to see if anyone else has done work in this area, do more pondering and thinking and note taking, talk it over with other people, etc. At some point it all gels together (when that happens it is almost magical and such an amazing moment of clarity) and then you are ready to use some sort of development process to actually write the code. Though by that point writing the code is extremely easy since you have such clear insight into what needs to be written. I love when that happens.