This document studies the distribution of activity among contributors to open source software projects. It analyzes three projects to determine if the Pareto principle applies, where 20% of contributors account for 80% of activity. Results show activity becomes more unequally distributed over time. For two projects, a limited core group performs most commits, emails, and bug changes. Future work aims to better understand how core groups evolve and identify new active contributors.

1. Evidence for the Pareto
principle in OSS Activity
Mathieu Goeminne & Tom Mens
Service de Génie Logiciel, Institut d’Informatique
Faculté des Sciences, Université de Mons
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2. Research topic
• Study of open source software evolution.
• Taking into account the community (social
network) of persons surrounding the
software project (developers, users).
• Looking for recurrent behaviour in this
community.
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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3. Goals
• Long-term goal
• Understand how software community and software
product/project co-evolve
• Provide guidelines and tools to support this
• Short-term goal
• Study of how development activity is distributed
over the different stakeholders.
• Find evidence for the Pareto principle in evolving
OSS.
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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4. Questions
• Is there a core group (of developers and/or
users) being significantly more active than the
others?
• How does the activity distribution evolve over
time?
• Is there an overlap between the different
activities?
• How does the activity distribution vary across
different projects?
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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5. Methodology
• Exploiting available data from source
code repositories, mailing lists and
bug trackers.
• Use of economy metrics measuring
distribution (in)equality.
• Empirical study of 3 OSS : Brasero,
Evince and Wine.
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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6. Econometrics
• Gini, Hoover, Theil (normalised) : express
inequality in a distribution.
• Values between 0 and 1
• 0 reflects a perfect equality
• 1 reflects a perfect inequality
• Have similar behaviors.
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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7. The 3 notions of
activities we used
• # commits done
• # mails sent
• # bug status changed
All of them are related to typical developer
activities
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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8. Activity distributions
(Gini index)
$"
!#," Brasero
!#+"
!#*"
!#)"
!#("
!#'" .4556/7"
Evince
!#&" 58697"
!#%" :;"0".<8=>?7"
!#$"
!"
-./0!)" 1230!*" -./0!*" 1230!+" -./0!+" 1230!," -./0!," 1230$!" -./0$!"
Wine
$" $"
!#," !#,"
!#+" !#+"
!#*" !#*"
!#)" !#)" 2.44536"
!#(" !#(" 47586"
!#'" 1233456" !#'" 9:;"<=>.<3"2?7@;=6"
!#&" 37486" !#&"
!#%" 9:;"/<.2/5"1=7>;<6" !#%"
!#$" !#$"
!" !"
-./0,," -./0!!" -./0!$" -./0!%" -./0!&" -./0!'" -./0!(" -./0!)" -./0!*" -./0!+" -./0!," -./0$!" -./0,+" -./0,," 1230!!" 1230!$" 1230!%" 1230!&" 1230!'" 1230!(" 1230!)" 1230!*" 1230!+" 1230!," 1230$!"
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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9. Pareto principle
• Most of the activity is carried out by a small
group of persons.
• Typically : 20% do 80% of the job.
• Doesn’t necessarily imply that the activity
distribution follows a Pareto law.
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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10. Pareto principle (cont.)
1
0.9
Brasero commits
0.8
0.7
mails
0.6
br changes
0.5
0.4
Evince
0.3
0.2
Wine
0.1
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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11. Core groups
• Display Venn diagrams of most active (top
20) persons, according to each definition of
activity.
• For each person, show the percentage of
activity attributable to this person.
• Use heuristics to take into account and
merge multiple identities representing the
same real person.
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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12. Core groups (cont.)
Brasero
Evince
Wine
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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13. Conclusions
• Activity distributions seem to become
more and more unequally distributed.
• The Pareto principle is clearly present in
studied projects.
• For Brasero and Evince, the activity is led
by a limited number of persons involved in
2 or 3 of the defined activities.
• For Wine, it seems not to be the case.
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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14. Future work
• Determine if the core group of a project
evolves over time.
• Use sliding windows to ignore inactive
persons and discover new active persons.
• Study “bus factor” and the persons involved.
• Automatic generation of Venn diagrams
including all persons involved in software
evolution.
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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15. Future work (cont.)
• Study correlation between community structure
(social network) and source code quality (as
computed using software metrics).
• Automatic statistical analysis to determine the
distributions fitting the data.
• Extend and refine types of activity. For instance:
• different types of commit activity (doc, source
code, test, etc.); of mail activity (information,
asking, answering, etc.); of bug repository activity
(bug creation, modification and commenting)
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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16. Thank you
Université de Mons Tuesday 2011-03-01, SQM workshop, Oldenburg, Germany Mathieu Goeminne & Tom Mens
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