Network Visualization by Semantic Substrates

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Network Visualization by Semantic Substrates

• Aleks Aris
• Ben Shneiderman

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Outline

• Graph Drawing Aesthetics
• Node Placement Methods
• Challenges of Network Visualization
• Semantic Substrates
• Demo
• Questions Answers

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Graph Drawing Aesthetics

• Minimize edge crossings
• Draw links as straight as possible
• Maximize minimum angle
• Maximize symmetry
• Minimize longest link
• Minimize drawing area
• Centralize high-degree nodes
• Distribute nodes evenly
• Maximize convexity (of polygons)
• Keep multi-link paths as straight as possible

Source 9 Davidson Harel
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Node Placement Methods

• Node-link diagrams
• Force-directed
• Geographical maps
• Circular layouts
• One or multiple concentric
• Temporal layouts
• Clustering
• Layouts based on node attributes (later)
• Matrix-based representations

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Force-directed Layout

• Also known as Spring
• Spreads nodes
• Minimizes chance of node occlusion

Source www.visualthesaurus.com
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Geographical Map
SeeNet, Becker et al.

• Familiar location of nodes

Source www.visualcomplexity.com (100)
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Circular Layouts (1 circle)
Schemaball, Martin Krzywinski

• Ex Schemaball
• Database schema
• Tables connected via foreign keys

Source http//mkweb.bcgsc.ca/schemaball/?home
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Circular Layouts (concentric)
Radial Tree Viewer, Nihar Sheth
Source www.visualcomplexity.com (26)
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Circular (concentric) Temporal
Hudson Bay Food Web
Source http//www.itk.ca/environment/tek-ecologic
al-foodweb-image.php
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Temporal Layout
Source 16 Garfield, Historiographic mapping
of knowledge
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Clustering
Vizster, Heer et al.
Source www.visualcomplexity.com (85)
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Hierarchical Clustering
Source 33 Schaffer, et al.
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Matrix-based Layout
VisAdj, Ghoniem et al.

• Ex VisAdj (Ghoniem, et al.)
• column source vertex
• row target vertex

Source 17 Ghoniem et al., IEEE
0-7803-8779-1/04
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Challenges of Network Visualization

• C1) Basic networks nodes and links
• C2) Node labels
• e.g. article title, book author, animal name
• C3) Link labels
• e.g. Strength of connection, type of link
• C4) Directed networks
• C5) Node attributes
• Categorical (e.g. mammal/reptile/bird/fish/insect)
  
• Ordinal (e.g. small/medium/large)
• Numerical (e.g. age/weight)
• C6) Link Attributes
• Categorical (e.g. car/train/boat/plane)
• Ordinal (e.g. weak/normal/strong)
• Numerical (e.g. probability/length/time to
  traverse/strength)

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C1) Basic Networks (nodes links)
Power Law Graph, Linyuan Lu

• Power Law Graph
• 5000 nodes
• Uniformly distributed

Source www.visualcomplexity.com (135)
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C1) Basic Networks (continued)
Vizster, Heer et al.

• Social friendship network
• 3 degrees from Heer
• 47,471 people
• 432,430 relations

Source www.visualcomplexity.com (97)
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C2) Node Labels
Internet Industry Partnerships, Valdis Krebs
Source www.visualcomplexity.com (168)
250 nodes

• Adding labels
• Nodes overlap with other nodes
• Nodes overlap with links

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C3) Link Labels
Netscan, Marc Smith

• Challenges
• Length
• Space
• Belongingness
• Distinction from other labels other types of
  labels

Source www.visualcomplexity.com (127)
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C4) Directed Networks
Yeast Protein Interaction

• Direction
• arrows
• labels
• Thickness
• color

SeeNet, Becker et al.
Source www.visualcomplexity.com (127)
Source 1 Becker et al.
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C5 C6) Node Link Attributes
CIA World Factbook Visualization, Moritz Stefaner
Source www.visualcomplexity.com (192)

• Value of node attribute indicated by node shape
• Value of link attribute indicated by a letter

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Semantic Substrates

• Group nodes into regions
• according to one attribute
• Categorical, ordinal, or binned numerical
• In each region
• place nodes according to other attribute(s)
• Advantages
• Location conveys meaning, interpretable
• Instant perception of
• different types of nodes
• their relative number
• connections between different groups of nodes
• Limitations
• Beyond 5 regions becomes challenging
• Constraint on nodes interferes with aesthetics

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Demo
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Thank you!
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Questions Answers
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(No Transcript)
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NVSS Network Visualization by Semantic Substrates
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Comparison with Fruchterman-Reingold
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Filtering Links by source-target
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Filtering links by time attribute (1)
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Filtering links by time attribute (2)
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Overlapped Links
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Three Regions

• Links from District Courts
• Indicates longevity of cases (short to long)
• District
• Circuit
• Supreme

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Scalability

• 1280x1024
• 1,122 nodes
• 7,645 links

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Using a third attribute in regions

• 13 circuits for both Circuit and District Courts
• Horizontally separated
• Reveals that links remain mostly within a circuit
  although there are some across (lateral citations)