1. Hierarchies (Trees) Definition Examples
Data repository in which cases are related to subcases
Examples
Family histories, ancestries
File/directory systems on computers
Organization charts
Animal kingdom: Phylum,…, genus,…
Object-oriented software classes
...
9/17/2018
Shengdong UofT

2. 9/17/2018
Shengdong UofT

3. 2 Main Approaches Connection (node & link) Containment (node in node)
outliner
Containment (node in node)
Venn diagram A B C A B C
9/17/2018
Shengdong UofT

4. Tasks Help understand node characteristics or tree structure?
Some kinds of tasks:
Find a node
Revisit node
List node ancestors
Understand local topology
Understand global topology
Different Trees are good for different tasks
9/17/2018
Shengdong UofT

5. Why is tree visualization hard?
Structure AND items (Structure harder, consumes more space)
Scaling: data size grows very quickly (exponential)
#nodes = bheight
How to provide Context (when focus changes)
May be multiple hierarchies
May be multiple focuses
9/17/2018
Shengdong UofT

6. Current Status Many 2D and 3D hierarchy visualizations
Each works for some tasks and some scales
Very few have had user testing
9/17/2018
Shengdong UofT

7. Node-Link Diagrams
9/17/2018
Shengdong UofT

8. Tree
9/17/2018
Shengdong UofT

9. Distortion: Graphical Fisheye - 1992
Sarkar & Brown, DEC SRC, CHI’92
Also a number of 2D network visualizations
Graphical Fisheye by Sarkar & Brown at DEC SRC in 1992
Generalization of Furnas fisheye view to 2D graph layout
Here the view on the right is the same structure, but focusing on node 48
9/17/2018
Shengdong UofT

10. Overview + Detail: PDQ Trees
Overview+Detail of 2D tree layout
Dynamic Queries on each level for pruning
9/17/2018
Shengdong UofT

11. PDQ Trees
9/17/2018
Shengdong UofT

12. Auto-arrangement + Thumbnail: Spacetree
9/17/2018
Shengdong UofT

13. Different Orientation & Refocus: Hyperbolic Trees
Rao, “Hyperbolic Tree”
Xerox PARC
Inxight
Focus+context
9/17/2018
Shengdong UofT

14. Space Optimized Tree Quang & Mao (InfoVis 2002)
9/17/2018
Shengdong UofT

15. 3D: Cone Trees Robertson, “ConeTrees” 3D for focus+context Xerox PARC
9/17/2018
Shengdong UofT

16. Space-Filling Representation
Each item occupies an area
Children are “contained” under parent
One example
9/17/2018
Shengdong UofT

17. Treemaps Shneiderman, “Treemaps” Vishal, Jeevak Maryland
Maryland
9/17/2018
Shengdong UofT

18. Variation: Cushion Treemap
Add shading and texture
to help convey structure
of hierarchy
Van Wijk ‘99
9/17/2018
Shengdong UofT

19. Sunburst Stasko, GaTech Radial layout Animated zooming 9/17/2018
Shengdong UofT

20. Sunburst vs. Treemap + Faster learning time: like pie chart
+ Details outward, instead of inward
+ Focus+context zooming
- Not space filling
- More space used by non-leaves
All leaves on 1-D space, perimeter
Treemap: 2-D space for leaves
- Smaller scale?
9/17/2018
Shengdong UofT

21. CHEOPS Beaudoin, “Cheops” Jon, Mudita
9/17/2018
Shengdong UofT

22. Challenges Multiple foci George Robertson, Microsoft Research
9/17/2018
Shengdong UofT

23. Time Tube - 1998 Chi et al., Xerox PARC, CHI’98 9/17/2018
In 1998, Chi et al at PARC introduced the Time Tube
A sequence of Disk Trees used to visualize changes in a web site over time
This is an example of viewing multiple similar hierarchies
9/17/2018
Shengdong UofT

24. Taxonomy Visualization - 2000
Graham et al., Napier Univ. IJHCS 2000
Recently, Graham et al at Napier Univ. explored visualizing changing biological taxonomies
In this example, individual objects are tracked across the hierarchies
Graham told me informally that this approach was abandoned when they tried to scale it up to real sized problems
9/17/2018
Shengdong UofT

25. MultiTrees - 1994 Furnas & Zacks, Bell Core, CHI’94
DAG’s with shared subtrees
MultiTrees were introduced by Furnas and Zacks at Bell Core in 1994
They are basically large DAG’s with shared subtrees
The typical example is about a class syllabus created by one professor
A second professor reuses some of the material, but only a subset
A third professor uses a different subset, possibly reusing some of the material introduced by the second professor
9/17/2018
Shengdong UofT

26. Polyarchies multiple inter-twined trees Visual pivot
George Robertson, Microsoft Research
9/17/2018
Shengdong UofT

27. Research Questions Can multidimensional data per node be portrayed?
How does the visualization scale?
What tasks are best supported by each vis?
Can users quickly understand the representation?
9/17/2018
Shengdong UofT

28. Observations Possible Solution
It’s hard to preserve the structure of the tree and allow scalability
Different approaches are good for certain tasks with certain scale, and one single approach often has limitations and can’t solve a range of problems well
Change of representations require learning
Possible Solution
Try a hybrid approach to balance the structure and scalability
Create a solution with continuous variations for a range of tasks
Use animation to help users to understand the representation
9/17/2018
Shengdong UofT

29. Node Link vs. Space Filling
Advantage of Node Link
Show Structure and Item
Natural
Disadvantage:
Hard to scale (100 nodes)
Advantage of Space Filling
Using 100% of screen space, scalable
monitoring and detect patterns in leaf nodes
Harder to see the structure
9/17/2018
Shengdong UofT

30. What about combining the two techniques to create a continuous series of smooth representations and use animation to help users to understand the these representations better
9/17/2018
Shengdong UofT

31. Several Ideas
Create animated transition between linked tree and treemaps
9/17/2018
Shengdong UofT

32. Intermediates
9/17/2018
Shengdong UofT

33. Overview + Detail
9/17/2018
Shengdong UofT

34. Questions Is this a worthwhile research topic?
Suggestions for further directions?
Any other combinations?
Which variation of the hybrid model is good for what tasks? (Scale?)
Anything else?
9/17/2018
Shengdong UofT