If every software project was fully specced, we'd do nothing but spend all our time writing specs. The best (and fastest) way to build something is with minima

If every software project was fully specced, we'd do nothing but spend all our time writing specs. The best (and fastest) way to build something is with minimal specs, and modifying as you go along. As your clients (internal or otherwise) actually get to use features as they are built, they'll provide tons of input that they wouldn't ever have put in a spec. This is also why you should never, ever, do fixed bid work in software development.