Rules in incomplete information systems

A new method of computing all optimal certain rules from an incomplete information system is presented and proved. The method does not require changing the size of the original incomplete system. Additionally, several existing rough set methods of computing decision rules from incomplete information systems are analyzed and compared. We show which of these methods are capable of generating all optimal certain rubs or a class of optimal certain rules and which methods may lead to generation of false rules. (C) 1999 Elsevier Science Inc. All rights reserved.