A method that solves a new problem by finding similar old cases.
CBR is like a car mechanic with a wall of old repair tickets. New weird rattle? He finds the closest old rattle, then tweaks the fix.
It uses old experience for new problems in support desks and diagnosis tools. Legal search uses it too.
KR
CBR needs cases to be written clearly before it can store, find, and adapt them.
IR
CBR first finds a similar old case, then adjusts the answer.
KNN
CBR and KNN both use similarity to borrow answers from nearby cases.
Expert System
CBR uses real cases to fill gaps left by hand-written rules.