Transcript
Page 1: Visualising Multiple Overlapping Hierarchies

Visualising Multiple Overlapping Hierarchies

Martin Graham, Jessie Kennedy, & Chris Hand

Napier University, Edinburgh

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Overview

IntroductionProblem DomainCurrent visualisation techniquesProposed TechniquesPrototypeConclusions

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Introduction

Taxonomy Royal Botanic Garden Edinburgh

Multiple overlapping hierarchiesIn general occur where a hierarchical

structure is re-organised Taxonomy (our domain) Document categorisation etc

No current visualisations support them

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What is a Taxonomy?

A methodology for classifying data. In our case, botanical specimens.

As knowledge increases or opinions change, new classification hierarchies (taxonomies) are published

These taxonomies co-exist. They do not replace each other.

Leads to accumulation of multiple overlapping taxonomies.

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Multiple Classifications

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Taxonomists need to..

Track a specimen across several classifications

View the progress of a group of specimens across classifications

Filter out unwanted pieces of information

We require a visualisation that can help taxonomists perform these tasks.

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Current paper-based taxonomy

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The problem

No current suitable paper-based method for inspecting multiple overlapping taxonomies

Investigate current computer-based visualisations

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Previous visualisations

Visualisations have been used for viewing hierarchical structures, e.g. file directories

Examples: Cone Trees - Robertson et al Information Pyramids - Andrews

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Cone Trees

© 1991 ACM - Cone Trees: Animated 3D Visualizations of Hierarchical Information - Copy by permission of the Association of Computing Machinery

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Andrews’ Information Pyramids

“Information Pyramids” is © IICM, Graz University of Technology, Austria

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Issues for Single Trees

Issues arising show that visualising even one tree has problems

Leaves displayed - internal structure masked

Space issuesOcclusion when 3D used

So visualising one tree is a problem

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Visualisation techniques for multiple trees

Two main techniques used: Animation - showing development over

timeHuang & Eades huge graphs

• also Wittenburg’s TreeViewer

Small Multiples - showing development over physical spaceChi’s Evolution of Web EcologiesTreemaps - Shneiderman & Johnson

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Huang’s on-line visualisation of a website

© Dept. of Computer Science and Software Engineering, University of Newcastle, NSW, Australia

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Chi et al’s Web Ecology Viewer

© User Interface Research Group - Xerox PARC

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Multiple TreeMap Comparison

© Human-Computer Interaction Laboratory, Dept. of Computer Science, University of Maryland, USA

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Issues for multiple trees

Animation Direct visual comparison between two

states only. Works best for gradual changes, not new

structures.Small Multiples

Lack of space on-screen due to repeating data

Lacks strong pre-attentive cues

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The Problem to be visualised

Need to develop appropriate visualisations to tackle these problems

Time/space trade-off

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Initial Design Sketch (1)

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Initial Design Sketch (2)

Ability to track a sub-tree (genus - grouping of specimens) across multiple hierarchies

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Initial Design Sketch (3)

Filter out unwanted pieces of information

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Prototype

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Conclusions

Need for visualising multiple hierarchies

Current visualisation techniques inadequate

Initial solutionsContinuing work

Prototyping User evaluation/feedback

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Acknowledgements

Royal Botanic Garden, EdinburghEPSRC

http://www.dcs.napier.ac.uk/~marting


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