Tree-Maps: Visualizing
Hierarchical Data
Hench Qian & Bill Shapiro
September 21, 1999
Problem
• Representing hierarchical data
– Structural information
– Content information
• Objectives
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Efficient Space Utilization
Interactivity
Comprehension
Esthetics
Favorite Sentence
• Most people come to understand the content
and organization of these structures
(hierarchical information) easily if they are
small, but have great difficulty if the
structures are large.
Traditional Methods
• Outlines (e.g., Windows Explorer)
Traditional Methods
• Tree Diagrams (WebView, University of Pittsburg)
• Text-based tools (e.g., ls in UNIX)
An Alternative: Tree-Maps
• Problems with traditional methods:
– Lots of dead space
– Difficult to represent large number of items
• Tree-Maps
– Utilize 100% of display space
– Scalable to thousands of items
Tree-Maps
How It Works
Example: TennisViewer
Critique
• Strengths
– Utilizes 100% of display space
– Shows relationships between nodes through size and
color
– Can effectively display large data sets
• Weaknesses
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Size comparison may be difficult
Cluttered display
Difficult to discern boundaries
Shows only leaf content information
Other Hierarchical Visualization
Tools
• Docuverse (University of Pittsburg)
– Containers (file directories) are shown as pie
segments
– Documents (files) are shown as colored dots
within pie segments
– Can represent a large number of items (~3000)
– Utilizes a fraction of the display space
-shows 3502 files in
164 directories
-pie segments
represent # of links
to each directory/file
-Color represents
age of files
Docuverse
Other Hierarchical Visualization
Tools
• Hyperbolic Trees (Xerox/Inxight)
– Dynamically warps display to zoom in on areas
of interest
– Good for interactive browsing
– Does not provide a good overview of the entire
dataset
– Demo