That's basically true, but I don't think anyone has a good general solution to unclear requirements besides constant communication and fine-tuning, a la XP/Agil

That's basically true, but I don't think anyone has a good general solution to unclear requirements besides constant communication and fine-tuning, a la XP/Agile. I like working on a module with interfaces and behaviors which are set in stone, but I find most of my work is a lot more exploratory than that, so the "clear requirements" can only come after it's about 90% done.