Chinese Journal of Computers   Full Text
Title	Visualization of Hierarchical Information Based on Venn Diagrams
Authors	WANG Wei-Xin1) MING Chun-Ying2) WANG Hong-An1) DAI Guo-Zhong1)
Address	1)(Intelligence Engineering Laboratory, Institute of Software, Chinese Academy of Sciences, Beijing 100080) 2)(Applied Science School, University of Science and Technology Beijing, Beijing 100083)
Year	2007
Issue	No.9(1632—1637)
Abstract &   Background	Abstract In order to visualize large-scale hierarchical information, an approach for tree visualization using nested circles is presented. The brother nodes of the tree are represented by the circles tangent to each other. The tree nodes at different levels are represented by nested circles. The properties of nodes are described by circle’s sites, sizes and colors. Circles at the same levels are packed closely together and no overlapping. The circle packing is very fast and robust. The complexity of circle packing algorithm is nearly liner. It is suitable for visualizing large information. This visualization provides not only good overviews for large-scale information but also the details for each node. Both the complex hierarchical structures and the properties of leaf nodes are obvious. The tree visualization is used to large file systems. Examples show this approach is robust, efficient and easy to use. keywords information visualization; hierarchical information; tree; nested circles; interaction technique background The visualization of hierarchical information structures is an important topic in the visualization community. Most of the work concentrated on the challenge to display large hierarchies in a comprehensible form. Various methods have been developed for this challenge, among which, node-link diagrams and space-filling visualization have been admittedly thought of as two classical methods. Node-link approach, which connects nodes with line segments in Euclidean space or hyperbolic space, represents the branches and leaves of a tree explicitly. However, the traditional node-link diagrams make poor use of the available display space. It does not give an effective overview of large hierarchies for only those nodes that expanded manually are visible. Among the space-filling approaches, there are rectangular space-filling techniques, such as Treemaps and its variations, and radial space-filling techniques. The Treemaps partitions the display space into a collection of rectangular bounding boxes representing the tree structure. It provides a good overview of large data sets. However, one drawback of Treemaps is that the hierarchical structure is hard to discern: Most of the space is used for the display of leaf nodes, and the branches are encoded implicitly. The radial space-filling techniques work well in revealing hierarchical structures with fan-shaped slices. But the peripheral slices with low aspect ratio in the radial display are difficult to distinguish sometimes. Now the Grokker visualization attracts much attention. It categorizes search results and displays them by circles containing subcategories in smaller circles or squares. It represents some categories well, but it does not give an overview of large data sets. The circles are not placed compact and many subcategories are invisible. It is necessary to click on a circle manually to expand and show its subcategories. Inspired by Treemaps and Venn Diagrams, the authors present a novel space-filling approach for tree visualization by using nested circles. It is similar to Treemaps, which provides good overviews for large hierarchical data sets. But it use nested circles instead of rectangles. It makes it easier to see groupings and structural relationships. This research is supported by the National Natural Science Foundation of China under grant No.60673195 and the National Basic Research Program (973 Program) of China under grant No.2006CB303100. This project 60673195 will research the optimization methods of visualization of hierarchical information based on nested circles to display large information in a limited space. This project will provide a complete solution for visualization of hierarchical information. It also provides a convenient interface and interaction techniques for browsing, searching and querying information. The research will enrich the theories and methods of human computer interaction. Furthermore the visualization and interaction are suitable for any hierarchical structures. The research of this paper is the main part of the project 60673195. It is to study the algorithm of packing large scale information efficiently. The result is the complexity of circle packing algorithm is nearly liner.