The undo function is not accessory, but still it has not been introduced to mobile devices in an appropriate way. Undo is still shaped to fit text editing, and it has changed a little only for graphical editing so far. In this paper, we report the results of a survey with which we investigated why and how to add this functionality to regular mobile phones – not only to smartphones or high-end handheld devices. Our respondents suggested an undo model that is linear, sequential, with variable granularity (according to the context of use) and requiring confirmation before execution (both to improve awareness and avoid additional mistakes).

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

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

3. Undo models
A coarse classification

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

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

6. 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

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

8. 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)

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

10. 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

11. 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

12. Highlights and
selected survey
items

13. 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

14. 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

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

16. 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

17. 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...

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

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

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

21. 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