Ron Jeffries: “The fundamental differences, as I see them, are two: first, XP [Extreme Programming] tries to stay silent on most issues while RUP [Rational Unified Process] wants to list and encompass all issues; second, XP is focused more on trust and RUP more on control. I don’t mean either of those terms in a strict or admonitory fashion, but hope that taking them metaphorically will give a taste of what I’m trying to express.”