Annals of Mathematics and Artificial Intelligence 39: 175–204, 2003.  2003 Kluwer Academic Publishers. Printed in the Netherlands. FlexiMine – A flexible platform for KDD research and application development R. Ben-Eliyahu-Zohary ∗ , C. Domshlak, E. Gudes, N. Liusternik, A. Meisels, T. Rosen and S.E. Shimony Department of Computer Science, Ben-Gurion University, P.O. Box 653, 84105 Beer-Sheva, Israel E-mail: ehud@cs.bgu.ac.il FlexiMine is a KDD system designed as a testbed for data-mining research, as well as a generic knowledge discovery tool for varied database domains. Flexibility is achieved by an open-ended design for extensibility, thus enabling integration of existing data-mining al- gorithms, new locally developed algorithms, and utility functions such as visualization and preprocessing. Support for new databases is simple and clean: the system interfaces with a standard database server via SQL queries and thus can handle any application database. With a view of serving remote, as well as local, users, internet availability was a design goal. By implementing the system in Java, minor modifications allow us to run the user-end of the system either as a Java applications or (with some limitations on the user) as a Java Applet. This paper reviews the architecture, design and operation of FlexiMine and presents some of the new ideas incorporated in the data-mining algorithms (Association rules, Decision trees, Bayesian knowledge-bases and Meta-queries). Keywords: knowledge discovery in databases, data mining, meta-queries, flexible software systems, WWW-based tools, association rules, Bayesian knowledge bases 1. Introduction With the enormous growth of accessible infromation around us, Data Mining and Knowledge Discovery (KDD) have become an important technology and research area [13]. FlexiMine is a prototype KDD system developed at Ben-Gurion University for testing and evaluating techniques and algorithms for Data Mining and Knowledge Dis- covery in the context of real-life databases and their users. The emphasis of this system and its software architecture is on the integration of many KDD operations (including database access and selection, preprocessing, data transformations such as abstraction, data-mining algorithms, and interactive visualization) and on extensibility. The system facilitates incorporation of new algorithms and supports convenient extensions to new databases or abstraction hierarchies. It preserves a friendly and easy to use interface which enables users and domain experts to access the system from both local and re- mote locations, and to evaluate results quality. ∗ Currently at the Department of Communication Systems Engineering, Ben-Gurion University, Israel.