A partial information supervisor that generates a class of closed controllable and observable sublanguages of a specified "legal" language is presented. This supervisor has the following features : 1) it can be implemented online (i.e., the disabled event set need only be computed once upon each event observation); 2) the computations of the disabled event set can be performed in O(mn) worst case complexity, where n is the number of states in the legal language generator and rn is the number of events; 3) an online supervisor presented previously by Heymann and Lin (1993) is a special case of the new supervisor; and 4) all the languages generated by the new supervisor contain the supremal closed controllable and normal (supCCN) sublanguage of the legal language (in fact, they contain a language del eloped by Fa et al. (1993) that was show n to contain the supCCN sublanguage).