Transcript
Page 1: Browsing Hierarchical Data  with Multi-level Dynamic Queries and Pruning

Browsing Hierarchical Data with

Multi-level Dynamic Queries and Pruning

By H. P. Kumar, C. Plaisant & B. Schneidernam

Presented by: Dawit Yimam Seid

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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


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