Undo for Mobile Phones
Does Your Mobile Phone Need an Undo Key? Do You?
Marco Loregian, University of Milano-Bicocca (Italy)
www.marcoloregian.net

Undo
• Well known function of PC
applications
• Allows to revert (the effects of)
commands
• Applied to user actions
• Different strategies

Undo models
A coarse classification

What does “undo”
mean when
operating with
mobile phones?

...and I really
mean phones,
not cool gadgets

The problem
• We need to know it in order to
design usable (successful) devices
• How should we find it out?
• Undo is a user intention
• We surveyed users

Concerns in mind
• Reversibility (yes/no)
• Criticality (high/low)

The survey
Online survey, 20 questions, 5 parts
1. Personal info (demographics)
2. Introduction (basic operations)
3. Scenario (multiple steps)
4. Reversed perspective
5. Conclusion (overall opinion)

The results
Full stats and comments in the paper
• Demographics
• Interesting facts from the survey

Demographics
146 respondents, 133 answered all questions
Age Distribution Gender
80
80
60
40 45%
36 55%
20
11 10
0 6
1 1 1 Male
15-20 21-25 26-30 31-35 36-40 41-45 46-50 51-55
Female

Number of phones used regularly
150,0
112,5 116
With respect to the
diffusion of mobile
75,0 phones, the sample is
consistent with Italian
37,5 population (istat.it)
25
0 1 4
none one two three more
Computer Skills (wrt applications)
60
54
52
Different computer 45
skills may indicate 39
30
familiarity with different
undo models
15
0 1
None Basic Average Advanced Absolute

Highlights and
selected survey
items

Confirmation
Prompt for confirmation
100
97
75
50
25 33
18
0
Yes No Yes, if...
66% want to know what they are undoing
22% ask for a transparent implementation
12% want to be warned in case of irreversibility

Granularity
Question 8 Question 10
110,0 70,0
102
61
82,5 52,5
47
55,0 35,0
27,5 17,5
27 17 18
13
0 4 0
1
Different preferences, variable granularity with
respect to different situations… context awareness?
The same key has different behaviors in different
moments, sometimes matching the End key

Timeline
• Very simple/intuitive interaction
• Linear and sequential undo
operations undone one-by-one in reverse chronological order

Privacy and
Responsibility
Can a SMS be deleted from your phone if you’ve not read it?
110,0
103
• Nothing hidden to 82,5
me
55,0
• The responsible
pays the price 27,5 31
0
Yes No

The verdict
Would you like mobile phones to have an undo key?
53
70 %
Ye
s
65
60
50
40
38
30 34
20
10
0
Yes No Yes, if...

Conclusion
• Undo for mobile phones:
linear, sequential, with
variable granularity and
confirmation before execution
• Generalization of the results

More work
• Undo for email, a.k.a. retraction
(poster yesterday)
• Undo for Ubiquitous Computing
published at UIC’08, IDC’2008

Moral of the talk
undo!
undo!
undo!
If we had more ctrl+Z
our lives might be better

Thank you,
any question?
Undo for Mobile Phones
Does Your Mobile Phone Need an Undo Key? Do You?
Marco Loregian, University of Milano-Bicocca (Italy)
www.marcoloregian.net