A large deviation principle for random elements in a Hausdorff space , at large-deviation speed , has a lower semicontinuous rate function . For every open set and every closed set ,
Equivalently, for every Borel set , the lower and upper bounds use its interior and closure, respectively. The conventions are and . A good rate function has compact sublevel sets for every finite . Here take ; the different speeds in the moderate deviation principle are stated explicitly when used.