The book aims to provide an objective evaluation of the available multi-dimensional visualization tools and their underlying techniques. The role of visualization tools in knowledge discovery, while acknowledged as an important step in the process is not clearly defined as to how it influences subsequent steps or exactly what the visualization reveals about the data before those steps take place. The research work described, by showing how known structures in test data sets are displayed in the visualization tools considered, indicates the definite knowledge, and limitations on that knowledge, that may be gained from those visualization tools. The major contributions of the book are: to provide an objective assessment of the effectiveness of some representative information visualization tools under various conditions; to suggest and implement an approach to developing standard test data sets on which to base an evaluation; to evaluate the chosen information visualization tools using the test data sets created; to suggest criteria for making a comparison of the chosen tools and to carry out that comparison.