My first workshop presentation, describing problems of multiple taxonomies in biology.

1. Visualising Multiple
Overlapping Hierarchies
Martin Graham, Jessie Kennedy, &
Chris Hand
Napier University, Edinburgh

2. Overview
Introduction
Problem Domain
Current visualisation techniques
Proposed Techniques
Prototype
Conclusions

3. Introduction
Taxonomy
Royal Botanic Garden Edinburgh
Multiple overlapping hierarchies
In general occur where a hierarchical
structure is re-organised
Taxonomy (our domain)
Document categorisation etc
No current visualisations support them

4. 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.

5. Multiple Classifications

6. 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.

7. Current paper-based
taxonomy

8. The problem
No current suitable paper-based method
for inspecting multiple overlapping
taxonomies
Investigate current computer-based
visualisations

9. Previous visualisations
Visualisations have been used for viewing
hierarchical structures, e.g. file directories
Examples:
Cone Trees - Robertson et al
Information Pyramids - Andrews

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

11. Andrews’ Information
Pyramids
“Information Pyramids” is © IICM, Graz University of Technology, Austria

12. Issues for Single Trees
Issues arising show that visualising even
one tree has problems
Leaves displayed - internal structure
masked
Space issues
Occlusion when 3D used
So visualising one tree is a problem

13. Visualisation techniques for
multiple trees
Two main techniques used:
Animation - showing development over time
Huang & Eades huge graphs
• also Wittenburg’s TreeViewer
Small Multiples - showing development over
physical space
Chi’s Evolution of Web Ecologies
Treemaps - Shneiderman & Johnson

14. Huang’s on-line visualisation
of a website
© Dept. of Computer Science and Software Engineering, University of Newcastle, NSW, Australia

15. Chi et al’s Web Ecology
Viewer
© User Interface Research Group - Xerox PARC

16. Multiple TreeMap Comparison
© Human-Computer Interaction Laboratory, Dept. of Computer Science, University of Maryland, USA

17. 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

18. The Problem to be visualised
Need to develop appropriate
visualisations to tackle these problems
Time/space trade-off

19. Initial Design Sketch (1)

20. Initial Design Sketch (2)
Ability to track a sub-tree (genus -
grouping of specimens) across multiple
hierarchies

21. Initial Design Sketch (3)
Filter out unwanted pieces of information

22. Prototype

23. Conclusions
Need for visualising multiple hierarchies
Current visualisation techniques
inadequate
Initial solutions
Continuing work
Prototyping
User evaluation/feedback

24. Acknowledgements
Royal Botanic Garden, Edinburgh
EPSRC
http://www.dcs.napier.ac.uk/~marting