Steve Betten
Catherine Plaisant
Ben Bederson

SpaceTree
Treemap

brightness = number of requests, no size coding i.e. layout stable as long as no page is added/removed

• Selected application: web site monitoring
• Monitoring:
– Look for patterns in web page requests over consecutive time periods
• Attribute value changes
• Simplification: only one attribute (mapped to color)
– Look for web pages that were created or deleted during those weeks
• Topology changes
• What are our options?

“Value” “Difference of values” brighter = more requests
• Might be more intuitive
• but requires to look at 2 values green = increase; red = decrease
(brighter = more change)
• Change is immediately visible
• OK for 2 periods only
• Not clear what happen when users need to integrate colors changes over several periods.

“All-at-once” “Slider”
• Less need to interact
• All data available on one screen
• Fewer pixels per webpage
• More pixels per page
• Generalizes to any number of periods

Value
Difference of values
All-at-once Slider

• “Show only when existing”
– Leads to layout shift
– Intuitive: does not show pages that did not exist!
• “Always show”
– Always show pages (colored black when non existing)
– Precludes using size coding
• In both cases, small icons can show location of changes

• 12 subjects (CS students)
– Each subject tested each version
• Training
– 10 min Treemap + 10 min each version
• Eight timed tasks
• Total duration: about 1 hour 30 minutes
• Computer generated datasets
– Most pages have small changes
– A small number of pages have significant changes

1. Determine if all the pages in a directory
grew in popularity
(2 tasks)
2. Find pages with specific patterns of requests e.g. up-down-up
(2 tasks)
3. Find deleted pages
4. Find created pages and determine if they were popular the first time they existed
5. Determine if a specific page grew in popularity every week (with no pages added i.e. no possible layout shifts)
6. Same as 5 with some pages added ( i.e. possible layout shift)

• For many questions, users perform equally well using any combination
• When searching for patterns
(e.g. up-down-up)
– “Difference of values” faster than “value”
– “Slider” faster than “all-at-once”
• In tasks where pages were created/deleted
– “Always show” faster than “show only when existing”
– Subjects strongly disliked layout shifts

• For many questions, users perform equally well using any combination
• When searching for patterns
(e.g. up-down-up)
– “Difference of values” faster than “value”
– “Slider” faster than “all-at-once”
• In tasks where pages were created/deleted
– “Always show” faster than “show only when existing”
– Subjects strongly disliked layout shifts

Value
Difference of values
All-at-once Slider

• For many questions, users perform equally well using any combination
• When searching for patterns
(e.g. up-down-up)
– “Difference of values” faster than “value”
– “Slider” faster than “all-at-once”
• In tasks where pages were created/deleted
– “Always show” faster than “show only when existing”
– Subjects strongly disliked layout shifts

• For many questions, users perform equally well using any combination
• When searching for patterns
(e.g. up-down-up)
– “Difference of values” faster than “value”
– “Slider” faster than “all-at-once”
• In tasks where pages were created/deleted
– “Always show” faster than “show only when existing”
– Subjects strongly disliked layout shifts

Value
Difference of values
All-at-once Slider

• For many questions, users perform equally well using any combination
• When searching for patterns
(e.g. up-down-up)
– “Difference of values” faster than “value”
– “Slider” faster than “all-at-once”
• In tasks where pages were created/deleted
– “Always show” faster than “show only when existing”
– Subjects strongly disliked layout shifts

• Disliked the layout shifts
• In both cases users mostly used the small icons to see location of changes

• “Difference of values” preferred over “value”
– Saves a step (visually determining the difference)
– Easier to see hue shifts than intensity changes
• “All-at-once” v. “slider”
– No difference
• Same pattern of preferences for
“ease of learning”
• Subjects only used details table to check their guesses based on color alone
• Very few errors
• Only half of subjects adjusted the time interval in the
“difference in values and slider” version
• User quote: “Different versions are suited to different tasks

• Treemaps can be effective for monitoring
• Consider using:
– “difference of values” instead of “value”
– “slider” with an option showing “all-at-once”
• Avoid size changes
• To download treemap3.2: www.cs.umd.edu/hcil/treemap3
(future versions will include monitoring capabilities described today)
• Partial support from Chevron-Texaco
• Participation of B. Shneiderman and J-D Fekete