ABSTRACT
Rough set theory is a mathematical theory founded by Dr. Z. Pawlak (1984) in order to properly deal with vague concepts. The basic idea of rough set theory is that, in contrast to precise concepts, vague concepts cannot be clearly characterized by available information. Kansei words such as beautiful and simple are vague concepts. The beauty of any product is a vague concept that we cannot always clearly dene from its attributes. Therefore, in rough set theory, a vague concept is replaced to the lower and the upper
CONTENTS
7.1 What Is Rough Set Theory? ...................................................................... 207 7.2 Theoretical Structure of Rough Set Theory ........................................... 210
7.2.1 Basics of Rough Set Theory .......................................................... 210 7.2.1.1 Decision Table .................................................................. 210 7.2.1.2 Approximations of Vague Concepts ............................ 211
7.2.2 Extended Rough Set Theory ......................................................... 212 7.2.2.1 Decision Table for Kansei Evaluation Data ................. 212 7.2.2.2 Kansei Approximation ................................................... 213 7.2.2.3 Extraction of Decision Rules .......................................... 215
7.2.3 Evaluation Measures of Decision Rules...................................... 216 7.2.4 Multilevel Framework for Kansei Design Rule Extraction ...... 217
7.3 An Application of Rough Set Theory ...................................................... 218 7.3.1 Kansei Evaluation Experiment .................................................... 218 7.3.2 Principal Component Analysis .................................................... 218 7.3.3 Customer Kansei Needs ............................................................... 219 7.3.4 Developmental Concept Rule .......................................................222 7.3.5 Product Design Rule ......................................................................222 7.3.6 Rule-Based Design System ........................................................... 224
References .............................................................................................................225
approximation of the vague concept. Lower approximation consists of all objects that surely belong to the concept, and upper approximation contains all objects that possibly belong to the concept. Two approximations are basic operations in rough set theory (Pawlak, 1998).
