Extreme Programming encourages adoption of all of its practices [extreme Programming]. In practice many projects drop practices. What remains can be an incomplete methodology, which is dangerous. This problem can be overcome by replacing each removed dropped practice with a compensating practice tailored to the circumstances of the project - effectively subclassing XP.
This experience report recounts the experiences of subclassing of XP at Wotif.com, where Pair Programming was replaced with "Pairing" and refactoring was replaced with "Team Refactoring."