ct 7 Currently there is an increasing interest in data mining and educational systems, making educational data mining as a new growing 8 research community. This paper surveys the application of data mining to traditional educational systems, particular web-based courses, 9 well-known learning content management systems, and adaptive and intelligent web-based educational systems. Each of these systems 10 has different data source and objectives for knowledge discovering. After preprocessing the available data in each case, data mining tech11 niques can be applied: statistics and visualization; clustering, classification and outlier detection; association rule mining and pattern min12 ing; and text mining. The success of the plentiful work needs much more specialized work in order for educational data mining to become 13 a mature area. 14 Ó 2006 Published by Elsevier Ltd.