[IEEE 2017 Joint 17th World Congress of International Fuzzy Systems Association and 9th International Conference on Soft Computing and Intelligent Systems (IFSA-SCIS) - Otsu, Japan (2017.6.27-2017.6.30)] 2017 Joint 17th World Congress of International Fuzzy Systems Association and 9th International Conference on Soft Computing and Intelligent Systems (IFSA-SCIS) - Modeling a fuzzy rule based expert system combining positive and negative knowledge for medical consultations using the importance of symptoms