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Hierarchies (Trees)
• Definition
• Data where cases relate to subcases
• Examples
• Family histories, ancestries
• File/directory systems on computers
• Organization charts
• Animal kingdom: phylum, genus
• Object-oriented software classes
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Common Tree Representations
Node-Link Containment
Alignment,
Adjacency
Outline
Treemap
Node-Link
Diagram
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Common Tree Representations
Node-Link Containment
Alignment,
Adjacency
Outline
Treemap Sunburst
Node-Link
Diagram
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Common Tree Representations
Node-Link Containment
Alignment,
Adjacency
Outline
Treemap Sunburst
Node-Link
Diagram Explorer
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Tree Visualization Challenges
• Structure AND data within items
• Scalability (exponential growth)
• Context (when focus changes)
• Multiple
hierarchies or
polyarchies
• Multiple
foci [Robertson]
[Furnas & Zacks]
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Tree Visualization Challenges
• Different local properties
• Topology (dense vs. sparse)
• Data content (image vs. text)
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Tree Visualization Challenges
• Different local properties
• Topology (dense vs. sparse)
• Data content (image vs. text)
• Dynamic data
• Hierarchies evolve
• Adjustment required for content,
context, topology
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Single Representation Limitations
Treemap Sunburst
Node-Link
Diagram Explorer
• Structure vs. data within items
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Single Representation Limitations
Treemap Sunburst
Node-Link
Diagram Explorer
• Structure vs. data within items
• Expressivity
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Single Representation Limitations
Treemap Sunburst
Node-Link
Diagram Explorer
• Structure vs. data within items
• Expressivity
• Static representation
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Single Representation Limitations
Treemap Sunburst
Node-Link
Diagram Explorer
• Structure vs. data within items
• Expressivity
• Static representation
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Node-Link & Treemap
Node-Link Treemap
Pros
• Familiar
• Shows both
structure and
items
• Scalable, space
efficient
• Eases comparison
of branch patterns
Cons
• Hard to scale
(100 nodes)
• Less familiar
• Hard to see
structure
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Node-Link & Treemap
Node-Link Treemap
Pros
• Familiar
• Shows both
structure and
items
• Scalable, space
efficient
• Eases comparison
of branch patterns
Cons
• Hard to scale
(100 nodes)
• Less familiar
• Hard to see
structure
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Node-Link & Treemap
Node-Link Treemap
Pros
• Familiar
• Shows both
structure and
items
• Scalable, space
efficient
• Eases comparison
of branch patterns
Cons
• Hard to scale
(100 nodes)
• Less familiar
• Hard to see
structure
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Node-Link & Treemap
Node-Link Treemap
Pros
• Familiar
• Shows both
structure and
items
• Scalable, space
efficient
• Eases comparison
of branch patterns
Cons
• Hard to scale
(100 nodes)
• Less familiar
• Hard to see
structure
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Solving the Problem
• Hybridize complementary
representations to balance structure
and scalability
• Representational adaptations for
branches and tasks
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Solving the Problem
• Hybridize complementary
representations to balance structure
and scalability
• Representational adaptations for
branches and tasks
• User manipulation and automatic
adjustment
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… … …
Node-Link TreemapHybrid 1 Hybrid 2
Elastic Hierarchy:
Entire set of adjustable hybrids
of multiple representations
Combine Multiple Representations
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y
x
Treemap (TM)
Node-Link (NL)
outside
inside
Taxonomy
NL outside NL
…….(A)
TM outside NL
…….(B)
NL outside TM
…….(C)
TM outside TM
…….(D)
NL inside TM
…….(E)
TM inside TM
…….(F)
NL inside NL
…….(G)
TM inside NL
…….(H)
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y
x
Treemap (TM)
Node-Link (NL)
outside
inside
Taxonomy
NL outside NL
…….(A)
TM outside NL
…….(B)
NL outside TM
…….(C)
TM outside TM
…….(D)
NL inside TM
…….(E)
TM inside TM
…….(F)
NL inside NL
…….(G)
TM inside NL
…….(H)
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y
x
Treemap (TM)
Node-Link (NL)
outside
inside
Taxonomy
NL outside NL
…….(A)
TM outside NL
…….(B)
NL outside TM
…….(C)
TM outside TM
…….(D)
NL inside TM
…….(E)
TM inside TM
…….(F)
Figure 4: here, the same tree is depicted 6 different ways
(illustration): in A, with a traditional node-link diagram, in F, with
a Treemap, and in B-E, with mixed, hybrid representations.
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y
x
Treemap (TM)
Node-Link (NL)
outside
inside
Taxonomy
Figure 4: here, the same tree is depicted 6 different ways
(illustration): in A, with a traditional node-link diagram, in F, with
a Treemap, and in B-E, with mixed, hybrid representations.
NL outside NL
…….(A)
TM outside NL
…….(B)
NL outside TM
…….(C)
TM outside TM
…….(D)
NL inside TM
…….(E)
TM inside TM
…….(F)
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y
x
Treemap (TM)
Node-Link (NL)
outside
inside
Taxonomy
Figure 4: here, the same tree is depicted 6 different ways
(illustration): in A, with a traditional node-link diagram, in F, with
a Treemap, and in B-E, with mixed, hybrid representations.
NL outside NL
…….(A)
TM outside NL
…….(B)
NL outside TM
…….(C)
TM outside TM
…….(D)
NL inside TM
…….(E)
TM inside TM
…….(F)
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Treemap Outside Node-Link
• Preserve top-level
topology
• Space filling at
crowded lower
levels
• Pattern comparison
among branches
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Node-Link Inside Treemap
• Local topology within context
• But, has tight space constrains
• More space if resizing is allowed
• But, resizing changes visual landmarks
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User Interactions
• Toggle between representations
• Pan, zoom
• Resize any subtree
• Unambiguous selection within
Treemaps using tabs
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Contributions
• Elastic representation
• Design space
… … …
Node-Link TreemapHybrid 1 Hybrid 2
Figure 4: here, the same tree is depicted 6 different ways
(illustration): in A, with a traditional node-link diagram, in F, with
a Treemap, and in B-E, with mixed, hybrid representations.
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Contributions
• Elastic representation
• Design space
• Interaction techniques
… … …
Node-Link TreemapHybrid 1 Hybrid 2
Figure 4: here, the same tree is depicted 6 different ways
(illustration): in A, with a traditional node-link diagram, in F, with
a Treemap, and in B-E, with mixed, hybrid representations.
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Acknowledgments
Ben Bederson, Ben Shneiderman,
Ravin Balakrishnan, Maneesh
Agrawala, Ed Chi, Amy Zhu, John
Hancock, Joe Laszlo, Jim Chengming
Cai, Noah Lockwood, Bowen Hui,
anonymous reviewers, and other IML
& DGP members at University of
Toronto