YouArentGonnaNeedIt (often abbreviated YAGNI, or YagNi on this wiki) is an ExtremeProgramming practice which states: "Always implement things when you actually need them, never when you just foresee that you need them." Even if you're totally, totally, totally sure that you'll need a feature later on, don't implement it now. Usually, it'll turn out either a) you don't need it after all, or b) what