Abstract: By employing one direction S-rough sets (one direction singular rough sets) and its dynamic characteristic, this paper presented the concepts of F-ladder knowledge and F-ladder degree. Using theses concepts, the discernibility theorem of F-ladder knowledge, the mining-discovery theorem of minimum F-ladder knowledge, the mining-discovery theorem of maximum F-ladder knowledge and the dependenccfilter theorem of knowledge discovery ere proposed, and the interior hiding principle of F-ladder knowledge, the mining-discovery criterion of F-ladder knowledge and its appli- canons were given. The results given in this paper show the new characteristics of one direction S-rough sets and the new applications of the dynamic characteristic of one direction trough sets.

Key words: One direction trough sets, F-ladder knowledge, F-ladder degree, Mining-discovery theorem, Mining-discovery criterion, Hiding principle, Application