I've heard that triangle put differently: time, cost and features. We're embarking on a major re-write of a legacy app. Before we started on this I had plans and specs as to what would go into the new app. I had some great features. Now I've learned that the deadline isn't moveable, and the cost is fixed, so now, only a month into the project I'm beginning to consider what features we can throw out, because clearly we're going to have to eliminate some features if we're to come in on time and on budget.