Gated development cycles were/are common, regardless of what you call them. If the target is not moving too fast, the process can work. If computer time is vastly more expensive than programmer time, working 'offline' writing/checking specs is time well-spent. If you take the standard SDLC steps, apply them to the smallest useful piece of functionality, replace written specs with automated tests, you get a single-piece flow model which strongly resembles agile practices (but says nothing about agile philosophy).
