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Browsing Hierarchical Data with
Multi-level Dynamic Queries and Pruning
By H. P. Kumar, C. Plaisant & B. Schneidernam
Presented by: Dawit Yimam Seid
5/10/2001 ICS 280 - Info Visualization 2
Tree Representations
• Node-link visualization– 2D (outline, tree diagrams)– 3D (Cone Trees)
• Tree-map visualization (nested & non-nested)• Graph structures (hypertext, flow charts, etc.)
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HDS/Tree Browsing
“Hierarchical browsing”– interaction matches structure– When do we do hierarchical browsing ?
• “hierarchical decision making”, iterative refinement/progressive querying of datasets
• e.g. sales & budget data, catalog of products, computer file systems
• most AND queries can be considered hierarchical
e.g. “SEX=male AND M_STATUS=single AND INCOME>=200,000”
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Tree Browsing - requirements
• Somewhat contradictory– Retain context - not getting lost deep in the tree
vs.– Don’t display non-relevant information
• How to achieve both at the same time ?
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PDQ Tree-Browser’s Approach
• Enable viewing tree at different levels• Selection (filtering) criteria at various levels in
the tree– attribute based specification of the foci of interest
• Hide uninteresting nodes and branches rapidly
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PDQ Tree-Browser Techniques
• Dynamic Queries & tight coupling– let users dynamically query nodes at each level– tightly couple query widgets to tree visualization– tightly couple the overview and detail views
• Automatic Pruning(in addition to zooming and panning)– automatically prune out uninteresting nodes/sub-
trees to get more compact views
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Dynamic Queries for Tree Browsing
• Applying DQ to trees is challenging !– Predefined relationships between data points
(unlike the case of flat/independent data sets). A query at one node affects other nodes
– Dynamic generation of widgets since • nodes at different levels can have different
attributes, and• since these nodes are dynamic
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The PDQ Tree-Browser Interface
• Data display - two resizable windows– Overview (left)– Detail view (right)
• Dynamic Query Panel– Attribute list (shows attributes of the current lowest
level)– Widgets panel - widgets created by users
• range-sliders (for numeric)• menu (for text)
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The PDQ Tree-Browser Interface
FeedbackIndicator
WidgetsPanelAttributes
List
Overview
Field-of-view
Detailedview
Level namebuttonLevel
increment/decrement
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Query & Manipulation• Query using Widgets
– Queries AND-ed together and matching nodes colored yellow in real time
• Manipulating a widget at an internal node level makes that node the current lowest level
• Tree structure changed through– level buttons– widgets– + or - buttons
• pan detail view dragging the field-of-view• Two types of coupling !
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Pruning
• Done when depth of the tree is increased.– Children of non-matching nodes are pruned
• Orange shows non-pruned nodes
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Example Application
The UniversityFinder
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PDQ Tree-Browser Limitations
• Max depth of 5• only up to 3 attributes to query; queries only
AND-ed• scrolling the overview needed when tree is
large• Clicking nodes in detail view do not open their
sub-trees
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Issues/Alternatives
• Pruning Vs. graying out ?• To change tree structure as widgets are
created or not ?• How to handle large trees ?
– Maintain overview to detail view coupling ?– Intermediate views, let user restrict before display
• How to generalize the PDQ Tree-Browser to other tree representations (e.g. treemap)– where to place widgets ? How to prune ?
• How to add OR and NOT queries ?
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Usability Testing
• 8 subjects (2 pilot, 6 test)• 7 tasks (feature based & task-based)• Results (on a scale of 1-9)
– 8.7 - pruning (+“Hide Grey Leaves”) is useful– 8.2 - dynamic query is useful– 4.8 - easiness of range-slider manipulation
• Some users did not like the dynamic widget creation !
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Controlled Experiment
Goal - compare Full-tree, Partially-pruned tree and Fully-pruned tree
• 25 subjects; 7 tasks• Results
– Task completion time
1. Fully-pruned 2. Partially-pruned 3. Full-tree– Subjective satisfaction rate
1. Partially-pruned 2. Fully-pruned 3. Full-tree– No clear cut finding on graying Vs. hiding pruned
nodes