Elastic Hierarchies: Combining Treemaps and Node-Link Diagrams

Shengdong Zhao, Michael J. McGuffin, Mark H. Chignell

University of Toronto

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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 ContainmentAlignment,Adjacency

Outline

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Common Tree Representations

Node-Link ContainmentAlignment,Adjacency

Outline

Node-LinkDiagram

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Common Tree Representations

Node-Link ContainmentAlignment,Adjacency

Outline

TreemapNode-LinkDiagram

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Common Tree Representations

Node-Link ContainmentAlignment,Adjacency

Outline

Treemap SunburstNode-LinkDiagram

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Common Tree Representations

Node-Link ContainmentAlignment,Adjacency

Outline

Treemap SunburstNode-LinkDiagram Explorer

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Tree Visualization Challenges

• Structure AND data within items• Scalability (exponential growth)• Context (when focus changes)• Multiple

hierarchies orpolyarchies

• 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 SunburstNode-LinkDiagram Explorer

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Single Representation Limitations

Treemap SunburstNode-LinkDiagram Explorer

• Structure vs. data within items

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Single Representation Limitations

Treemap SunburstNode-LinkDiagram Explorer

• Structure vs. data within items• Expressivity

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Single Representation Limitations

Treemap SunburstNode-LinkDiagram Explorer

• Structure vs. data within items• Expressivity• Static representation

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Single Representation Limitations

Treemap SunburstNode-LinkDiagram 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

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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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Combine Multiple Representations

Node-Link

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Node-Link Treemap

Combine Multiple Representations

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Node-Link TreemapHybrid 1

Combine Multiple Representations

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Node-Link TreemapHybrid 1 Hybrid 2

Combine Multiple Representations

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… … …

Node-Link TreemapHybrid 1 Hybrid 2

Combine Multiple Representations

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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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Elastic Hierarchy

Node–Link Diagram

A tree of ~3500 nodes using Node-Link

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Elastic Hierarchy

Treemap

Same tree using Treemap

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Elastic Hierarchy

Same tree using Elastic Hierarchy

Elastic Hierarchy

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Elastic Hierarchy

Node–Link Diagram Treemap Elastic Hierarchy

• Elastic Hierarchy• Focus+context• Adaptability+user control• Multiple foci

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y

x

Taxonomy

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y

x Treemap (TM)

Node-Link (NL)

Taxonomy

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y

x Treemap (TM)

Node-Link (NL)

outside

inside

Taxonomy

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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

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Treemap Outside Node-Link

• Preserve top-level topology

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Treemap Outside Node-Link

• Preserve top-level topology

• Space filling at crowded lower levels

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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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Treemap/Node-Link Outside Treemap

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• Focus+Context

Treemap/Node-Link Outside Treemap

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• Focus+Context• Multiple foci

Treemap/Node-Link Outside Treemap

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• Focus+Context• Multiple foci • Occlusion

Treemap/Node-Link Outside Treemap

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Node-Link Inside Treemap

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Node-Link Inside Treemap

• Local topology within context• But, has tight space constrains

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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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Working Together

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Working Together

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Implementation

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Implementation

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Implementation

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Implementation

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Implementation

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User Interactions

• Toggle between representations

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User Interactions

• Toggle between representations• Pan, zoom

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User Interactions

• Toggle between representations• Pan, zoom• Resize any subtree

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User Interactions

• Toggle between representations• Pan, zoom• Resize any subtree• Unambiguous selection within

Treemaps using tabs

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Elastic Hierarchy Video

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Contributions

• Elastic representation

… … …

Node-Link TreemapHybrid 1 Hybrid 2

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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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Future Work

• Empirical evaluation • Other useful elastic 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

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Questions

Node–Link Diagram Treemap Elastic Hierarchy