visualising multiple overlapping hierarchies
DESCRIPTION
My first workshop presentation, describing problems of multiple taxonomies in biology.TRANSCRIPT
Visualising Multiple Overlapping Hierarchies
Martin Graham, Jessie Kennedy, & Chris Hand
Napier University, Edinburgh
Overview
IntroductionProblem DomainCurrent visualisation techniquesProposed TechniquesPrototypeConclusions
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
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.
Multiple Classifications
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.
Current paper-based taxonomy
The problem
No current suitable paper-based method for inspecting multiple overlapping taxonomies
Investigate current computer-based visualisations
Previous visualisations
Visualisations have been used for viewing hierarchical structures, e.g. file directories
Examples: Cone Trees - Robertson et al Information Pyramids - Andrews
Cone Trees
© 1991 ACM - Cone Trees: Animated 3D Visualizations of Hierarchical Information - Copy by permission of the Association of Computing Machinery
Andrews’ Information Pyramids
“Information Pyramids” is © IICM, Graz University of Technology, Austria
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
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
Huang’s on-line visualisation of a website
© Dept. of Computer Science and Software Engineering, University of Newcastle, NSW, Australia
Chi et al’s Web Ecology Viewer
© User Interface Research Group - Xerox PARC
Multiple TreeMap Comparison
© Human-Computer Interaction Laboratory, Dept. of Computer Science, University of Maryland, USA
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
The Problem to be visualised
Need to develop appropriate visualisations to tackle these problems
Time/space trade-off
Initial Design Sketch (1)
Initial Design Sketch (2)
Ability to track a sub-tree (genus - grouping of specimens) across multiple hierarchies
Initial Design Sketch (3)
Filter out unwanted pieces of information
Prototype
Conclusions
Need for visualising multiple hierarchies
Current visualisation techniques inadequate
Initial solutionsContinuing work
Prototyping User evaluation/feedback
Acknowledgements
Royal Botanic Garden, EdinburghEPSRC
http://www.dcs.napier.ac.uk/~marting