Abstract: The preferential process knowledge is the most important knowledge which the decision-makers and the desig- ners are concerned with. As to the complex characteristics of the process attributes, it utilizes the extended rough set model, extends the classical rough set model used for knowledge disc-overy and discovers the preferential process knowledge with indiscernibility relation, similarity relation and dominance relation synthetically, I.e. multiple relations. Secondly, it presents some key methods and algorithms, such as the pretrea- tment methods and reduction algorithm for the process attribu- tes, the presentation of the preferential rules and induction algo-rithm of the preferential knowledge. Finally, an instance is verified based on the process information table of the bore mac-hining. The result proves that the preferential process knowle- dge discovered based on the extended rough set model is the key one that can guard the decision-makers to carry out decisio-ns directly and efficiently, for it has left out the evaluation proc-edure of the process rules based on support, confidence and certainty.

Key words: Knowledge discovery, Preferential knowledge, Process planning, Rough set