Visualizing Relationsin Hierarchical Data

Presented by

Soha Makady

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Problem?• Dataset examples:

– A text book• Hierarchy: Book, chapters, sections, paragraphs,

…etc.• Relation: A section can be a pre-requisite for

understanding another section

– A software system:• Hierarchy: System, packages, classes, methods• Relations: inheritance, method calls …etc.

• How to visualize hierarchical and non-hierarchical relations in ONE visualization?

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ArcTrees: Visualizing Relations in Hierarchical DataP. Neumann, S. Schlechtweg, S. Carpendale.

Proceedings of Eurographics, IEEE VGTC Symposium on Visualization (EuroVis2005)

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ArcTrees – Basic Idea• Designed for viewing digital media• Represents the hierarchical structure by a

spanning tree• Represents the non-hierarchical relations by

edges/arcs• Play video*

4* Available from: http://innovis.cpsc.ucalgary.ca/Research/ArcTrees

ArcTrees - Hierarchy Visualization

• Node weight metric:– Used to calculate the size of a node– Can be a structural metric (e.g. size based on number

of children)– Can be a semantic metric (e.g. size based on number of

pages, chapter importance)

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ChapterChapter

SectionSub-section

ArcTrees - Hierarchy Visualization

• Color coding:– Clarifies the different levels in the hierarchy

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ArcTrees - Relations Visualization

• Arcs are controlled in height to better utilize space• Transparent arcs connect collapsed nodes

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Node1

Node3

Node2 (Expanded)

ArcTrees - Relations Visualization

• Arc weight metric:– Used to calculate the width of an arc– Can be structural or semantic– The width can indicate many relations between two nodes

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ArcTrees – Interaction – Zoom & Filter

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ArcTrees – Interaction – Focus + Context

• Glyph:– Indicates hidden relations– The diameter stands for the number of hidden

relations

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Several connections

Glyph

Click on arc

ArcTrees – Interaction – Focus + Context

11Hidden relations within Ch(16) of Glyph

Expanded relations between Ch 15 & 16

ArcTrees in Acrobat Reader

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Hierarchical Edge Bundles:

Visualization of Adjacency Relations in Hierarchical DataDanny Holten

InfoVis06, 2006

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Hierarchical Edge Bundles

• Augments existing tree visualizations• Based on bundling the relations’ edges hence

reducing visual clutter

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Relations within a Radial Layout

• Visualizes a call graph in a software system (caller in green, callee in red)

• Shows sparsely connected systems15

Bundling Strength

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Shows node-to-node connectivity

Bundles reduce visual clutter

Shows implicit relations between parents

Bundle-based Interaction

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User can inspect individual curves

Other Hierarchical Representations?

• Works for radial layout, balloon layout and treemaps

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ArcTrees

Advantages• Edge crossing reduced (by arc

width)• Visual clutter reduced by

opacity• Uses little screen space• Clear

Limitations• Is it generic?• Scaling for large hierarchies?• Can it show patterns?• Can we follow paths?

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Hierarchical Bundles

Advantages

• Visual clutter reduced

• It is generic

• It can show patterns of sparse/dense data

Limitations

• Bundles lead to losing information about edges’ numbers/weight/structure

• Ambiguous

• Can we follow paths?

Related Work: I. Software Landscapes*

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Package(s)

Class

* M. Balzer et al., Software Landscapes: Visualizing the Structure of Large Software Systems. In Proc. Eurographics 2004, IEEE

Related Work: I. Software Landscapes*

* M. Balzer et al., Software Landscapes: Visualizing the Structure of Large Software Systems. In Proc. Eurographics 2004, IEEE

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Relation(s)

• Occlusion?• Ambiguity?

Related Work – II. TimeRadarTrees*

* M. Burch and S. Diehl, TimeRadarTrees: Visualizing Dynamic Compound Digraphs. In Proc EuroVis2008

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Edge 3

Edge 2

Edge 1

Edge 2

Edge 3

Edge 1

Related Work – TimeRadarTrees*

* M. Burch and S. Diehl, TimeRadarTrees: Visualizing Dynamic Compound Digraphs. In Proc EuroVis2008 23

TimeRadarTrees*

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• Eliminates edge crossing• Readability?

My Project: Methods call graphs• Hierarchical relationships:

– Packages, classes, methods

• Non-hierarchical relationships:– Method calls (m1 calls m2 calls m3 …)

• Can I use ArcTrees? (Bundles … No way!)

• Call graph may include repeated branches

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mg()mb() ma()

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Package 1

Package 2Package 3

Package 4

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class1

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Click on a method to find affected methodsm1

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Package 1

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class1

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Legend

Direct

Level 2 to 4

Lowerthan 4

Package 2

Calling Structure: Pie-Tree/Sunburst Tree

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mg()mb() ma()

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