This is not the first book on rough set analysis and certainly not the first book on knowledge discovery algorithms, but it is the first attempt to do this in a non-invasive way. In this book the authors present an overview of the work they have done in the past seven years on the foundations and details of data analysis. It is a look at data analysis from many different angles, and the authors try not to be biased for - or against - any particular method. This book reports the ideas of the authors, but many citations of papers on Rough Set Data Analysis in knowledge discovery by other research groups are included as well.