I think one of the major benefits of an agile-like process is that, in theory, so long as things don't sit in the backlog/icebox for months, all your requiremen

I think one of the major benefits of an agile-like process is that, in theory, so long as things don't sit in the backlog/icebox for months, all your requirements are short-lived. The “hack it, deliver, repeat” process actually benefits the requirements gathering process because you only need short-term requirements; you don't need to understand what the product needs to do a long way out because there's an implicit understanding that whatever the product is in the future will be changed to meet future requirements. The really important thing about requirements in an agile process is that you need a set of documents that accurately describe what the product is supposed to be doing right now. Using the stories doesn't work because you have to look through everything from the beginning to build up a picture of what a feature is, and using the code doesn't work in case someone has mis-understood the requirements. Managing the change through the project is the hard bit.