Revisiting the Applicability of the Pareto Principle to Core Development Teams in Open Source...

Is the Pareto Principle Applicable to the Core Teams

of GitHub Projects?

KazuhiroYamashita

YasutakaKamei

ShaneMcIntosh

NaoyasuUbayashi

Ahmed E. Hassan

Core developers play a critical role

in software development

2

Core developers are responsible for guiding and coordinating the development of an OSS project.

The most productive developers who have made roughly 80% of the total contributions.

Nakakoji

Mockus

In fact, some argue that core developers in OSS projects follow the Pareto Principle

5Effort Result

80% 80%

20%20%

Pareto Principle in Software Development

6

20％

80％ 20％

80％

ProjectDevelopers Artifacts

Prior studies have arrived at mixed conclusions about core teams and the Pareto Principle

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Pareto Non-Pareto

Goeminne IWSQM

RoblesRAMSS

MockusTOSEM

GeldenhuysECSEAA

KochISJ Dinh-Trong

TSE

The results depend on small number of case study systems

Other

Prior studies have arrived at mixed conclusions about core teams and the Pareto Principle

8

< 10 or 15 Other

Goeminne IWSQM

RoblesRAMSS

MockusTOSEM

GeldenhuysECSEAA

KochISJ

Dinh-TrongTSE

Overview of our study of core teams on GitHub

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Applicability of the Pareto PrincipleNumber of Core Developers


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Core and Non-Core Developers Activities


Collecting and analyzing GitHub data to study core team activity

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Filter Heuristics

Core

Non-Core

Core

Non-Core

Calc Prop

Projects

Core

Non-CoreClassifyCommits

Core Team Size Activity


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Filter Heuristics

Core

Non-Core

Projects

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Core

Non-Core

Calc Prop

Core



Preprocessing GitHub data to handle forks, duplicates, and to remove immature projects

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8,510,504 repositories -> 2,496 repositories


24

Filter Heuristics

Core

Non-Core

Projects

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Core

Non-Core

Calc Prop

Core



Using heuristics to identify core team members

26Commit-based LOC-based Access-based

Core Core Core

29A B C D

Our commit-based core contributor heuristic

Number of Commits

= Commit

Step1: Sort contributors by their number of commits

30A BC D

Number of Commits

Step2: Compute the proportion of commits that each contributor

32A BC D

60% 20% 10% 10%Commits ratio

Step3: Core contributors are those developers below the 0.8 cumulative contribution cutoff

33A BC D

0.8

1.0

0.6

Cumulativeratio

Pct. CoreDev2/4*100 = 50%

Num CoreDev2


35

Filter Heuristics

Core

Non-Core

Projects

35

Core

Non-Core

Calc Prop

Core




36




37




38

Filter Heuristics

Core

Non-Core

Projects

38

Core

Non-Core

Calc Prop

Core



Our approach to study Core Team Size

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30%20%10%Percentage of Core Devs

Compliance with the Pareto Principle

Stratify projects along the confounding factors

Small Medium Large Small Medium Large Small Medium LargeLOC Total Author Age

The example project does not follow the Pareto Principle

Core team proportions are widespread

43

Commit-based Divide by LOC

Often, there are fewer than 15 core developers in a projects

44

Number of core developers in projects

88% 98% 96%Commit-Based LOC-Based Access-Based


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More than half projects do not follow the Pareto principle

Most of projects have 15 or less core developers


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49

Filter Heuristics

Core

Non-Core

Projects

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Core

Non-Core

Calc Prop

Core



Our approach to study activity

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By using the keywords, we classify the commits.

DevelopmentActivity Type KeywordsForward Engineering implement, add, requestMaintenanceReengineering optimiz, adjust

Corrective Engineering bug, fix, issue, error

Management license, formatting, TODO

No big differences in proportions of development activities

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Commit-Based LOC-Based Access-Based


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There are no big differences between

core and non-core activities


56





There are no big differences between

core and non-core activities

Extremely large core team may be interesting

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Heuristic -15 16-20 21-50 51-100 101-

Commit-Based

2,197 98 137 17 47

LOC-Based

2,454 15 13 4 10

Access-Based

1,164 24 24 0 0

Many projects face a risk of bus factor

59

Commit-Based LOC-Based Access-Based43% (Core=1: 8%) 81% (Core=1: 24%) 54% (Core=1: 21%)

In fact, most of projects have less than 5 core developers

Conclusion

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Core Developer• additional slides

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Additional description of our definition

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0.8

1.0

A B C D E Depend on Name

Commit-based

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Age Total Author

LOC-based

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Age Total Author

LOC

Access-based

69

Age Total Author

LOC

Data Extraction

70


Data Extraction

71

Data Extraction

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(1) Filter projects by GHTorrent

Filter forked repositories.

Fork

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One of the features of GitHub

Fork (clone)

Original Repository

Fork Repository

Pull Request

Data Extraction

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Filter less than 10 devs repositories.

Data Extraction

75




Filter repositories which is developed outside of GitHub.

Data Extraction

76




Filter repositories which is developed outside of GitHub.


Data Extraction

77

Data Extraction

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(2) Clone repositories

4,618 repositories -> 4,154 repositories

local server

clone

Data Extraction

79

Data Extraction

80

(3) Filter duplicate projects

Project A Fork of Afork

clone

Project Bregister

Clone of A

Data Extraction

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(3) Filter duplicate projects


Project A Project B

Compare SHAs

c87cce1e1a7260f40ccb5455e44c8b67f28651fa5e

655b8be757dd93a4cf3718145880cf484e34e63bde

Data Extraction

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Data Extraction

83

(4) Calculate metrics

LOCTotal CommitsTotal Authors

AgeRepository

Data Extraction

84

Data Extraction

85

(5) Filter projects by metrics



Filter less than 1,000 LOC repositories.

Revisiting the Applicability of the Pareto Principle to Core Development Teams in Open Source...

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