"Criterium" is a kind of bicycle race on a short course with many laps, periodic "primes," and that usually ends in a sprint finish. A rider that can stay near the front of the pack tends to use less energy sprinting out of the corners as the pack slows to enter them; a rider near the back of the pack is both susceptible to fatigue and getting caught in any crashes that may happen. Ahh, bike racing. I do miss it so! The word the authors of the multi_index docs were looking for is "criterion," or, when pluralized, "criteria." -- Dave Abrahams Boost Consulting www.boost-consulting.com