Int. J. Intelligent Systems Technologies and Applications, Vol. 12, Nos. 3/4, 2013 283 Copyright © 2013 Inderscience Enterprises Ltd. An evolutionary approach to discover intra- and inter-class exceptions in databases Jyoti Vashishtha*, Dharminder Kumar and Saroj Ratnoo Department of Computer Science & Engineering, Guru Jambheshwar University of Science & Technology, Hisar, Haryana, India Email: jyoti.vst@gmail.com Email: dr_dk_kumar_02@yahoo.com Email: ratnoo_saroj@gmail.com *Corresponding author Abstract: Data mining algorithms produce information of a statistical nature that contains accurate and reliable knowledge. However, in many cases these algorithms do not discover hidden facts which may be interesting to users. Therefore, the recent aim of knowledge discovery in databases (KDD) is to expose patterns that are exceptions to the existing knowledge. Exceptions are considered interesting as they add extraordinary facts to the knowledge base and create an incentive in users to re-examine their decisions. Discovering exceptions along with the decision rules increases the quality of decision making in those rare circumstances where the rules are not applicable. This paper is an attempt to devise a framework to discover exceptions using an evolutionary approach. In this work, we have categorised exceptions as inter and intra class. Experimental results are presented to demonstrate the performance of the proposed algorithm. Keywords: data mining; discovery of interesting rules; exception discovery; intra class exceptions; inter class exceptions; evolutionary approach; genetic algorithms; knowledge discovery. Reference to this paper should be made as follows: Vashishtha, J., Kumar, D. and Ratnoo, S. (2013) ‘An evolutionary approach to discover intra- and inter- class exceptions in databases’, Int. J. Intelligent Systems Technologies and Applications, Vol. 12, Nos. 3/4, pp.283–300. Biographical notes: Jyoti Vashishtha is an Assistant Professor at the Department of Computer Science & Engineering in Guru Jambheshwar University of Science and Technology, Hisar, India. She is pursuing PhD in Computer Science from the Department of Computer Science and Engineering, Guru Jambheshwar University of Science and Technology, Hisar. Her research interests include intelligent systems, knowledge discovery and data mining and machine learning. Dharminder Kumar is Professor and Chairperson of the Department of Computer Science & Engineering, Guru Jambheshwar University of Science and Technology, Hisar. His current research interests include data warehouse and mining and machine learning. He has published widely in international journals and proceedings of international conferences in these areas. Saroj Ratnoo is working as Professor at the Department of Computer Science & Engineering in Guru Jambheshwar University of Science and Technology,