Browsing hierarchical data with multi-level dynamic queries and pruning

Users often must browse hierarchies with thousands of nodes in search of those that best match their information needs. ThePDQ Tree-browser(Pruning with Dynamic Queries) visualization tool was specified, designed and developed for this purpose. This tool presents trees in two tightly-coupled views, one a detailed view and the other an overview. Users can use dynamic queries, a method for rapidly filtering data, to filter nodes at each level of the tree. The dynamic query panels are user-customizable. Sub-trees of unselected nodes are pruned out, leading to compact views of relevant nodes. Usability testing of the PDQ Tree-browser, done with eight subjects, helped assess strengths and identify possible improvements. The PDQ Tree-browser was used in Network Management (600 nodes) and UniversityFinder (1100 nodes) applications. A controlled experiment, with 24 subjects, showed that pruning significantly improved performance speed and subjective user satisfaction. Future research directions are suggested.