Activity-Based Analysis of Open Source Software Contributors: Roles and Dynamics

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Activity-Based Analysis of Open Source Software
Contributors: Roles and Dynamics
Jinghui Cheng
Department of Computer and Software Engineering
Polytechnique Montreal, Montreal, Canada
jinghui.cheng@polymtl.ca
Jin L.C. Guo
School of Computer Science
McGill University, Montreal, Canada
jguo@cs.mcgill.ca
Abstract—Contributors to open source software (OSS) com-
munities assume diverse roles to take different responsibilities.
One major limitation of the current OSS tools and platforms
is that they provide a uniform user interface regardless of
the activities performed by the various types of contributors.
This paper serves as a non-trivial first step towards resolving
this challenge by demonstrating a methodology and establishing
knowledge to understand how the contributors’ roles and their
dynamics, reflected in the activities contributors perform, are
exhibited in OSS communities. Based on an analysis of user
action data from 29 GitHub projects, we extracted six activities
that distinguished four Active roles and five Supporting roles of
OSS contributors, as well as patterns in role changes. Through
the lens of the Activity Theory, these findings provided rich design
guidelines for OSS tools to support diverse contributor roles.
Index Terms—open source software, open source community,
activity-based analysis, contributor roles
I. INTRODUCTION
As a software development model, OSS has experienced
a fast growth during the past decades. The communities
around OSS projects are becoming increasingly heteroge-
neous, comprising not only developers and tech-savvies but
also designers, managers, and users with a wide-ranging level
of experience and expertise. As a result, the ways participants
contribute to the OSS projects also become increasingly di-
verse [7], [12]. However, one major limitation of the current
OSS tools and platforms is that they provide a uniform user
interface regardless of the activities performed by the various
types of contributors interacting with the platform. In other
words, the current OSS tools do not take into enough account
the various roles assumed by the OSS contributors.
This paper serves as a non-trivial first step towards re-
solving this challenge by demonstrating a methodology and
establishing knowledge to understand how the roles and their
dynamics are currently exhibited in OSS communities. In
particular, we focused on examining the roles and their dy-
namics based on the types of activities that OSS contributors
perform. This perspective is inspired by several aspects of
the Activity Theory [24]. Particularly, the Activity Theory,
applied to the field of Human-Computer Interaction, specifies
that information and communication tools need to focus on
mediating human activities, facilitating users to perform a
group of low-level actions and operations in order to achieve
higher-level objectives; additionally, such mediation needs to
be adjustable in an evolving context [20]. To guide our study,
we pose the following research questions:
RQ1: What are the decisive activities that distinguish the roles
assumed by OSS contributors?
RQ2: What are the prominent roles that can be identified
through analyzing a wide range of actions community
contributors perform in a diverse set of projects?
RQ3: How do the roles assumed by the community contrib-
utors in an OSS project change over time?
To answer these questions, we collected and analyzed action
data of 20,838 unique contributors from 29 diverse GitHub
projects and conducted factor and clustering analyses to iden-
tify the prominent activities and roles of OSS contributors.
In the following sections, we first briefly review the related
work (Section II). We then outline our data collection and
analysis methods (Section III). In Section IV, we report our
results on the identified activities and roles, as well as the
role dynamic patterns. We then discuss the implications of
our findings to the design of OSS tools (Section V). Finally,
we provide concluding remarks in Section VI
II. RE LATE D WORK
Our study is related to previous work that focused on users’
roles in information and communication technologies (ICTs)
and studies that investigated the structure of OSS communities.
A. Role-Based Approaches in ICTs
Previous work has explored models and techniques to
identify and support different roles in ICTs of various ap-
plication domains, including collaboration tools [4], access
control systems [5], knowledge co-production platforms [3],
and software engineering tools [1], [27]. For example, Arazy et
al. [3] identified seven roles of Wikipedia contributors, such as
all-round contributors and layout shapers, through a clustering
analysis of user actions in Wikipedia articles.
Our study is most closely related to previous work that
investigated roles in tools and techniques that support software
design and development [23]. Zhu et al. [27] advocated a
complete and consistent role consideration in all aspects of
software engineering and in research about tools through the
lens of Role-Based Software Development (RBSD). Acu˜
na
and Juristo [1] also proposed a model that consists of 20 gen-
eral capabilities crucial in software development and mapped
arXiv:1903.05277v1 [cs.SE] 13 Mar 2019

these capabilities with 20 predetermined roles in software
projects. Leveraging this model, they presented a procedure
for assigning people to roles according to their capabilities.
More recently, researchers investigated role dynamics in
self-organized software development teams. Hoda et al. [13]
conducted Grounded Theory research involving 58 agile prac-
titioners from 23 software organizations to understand the
role dynamics in agile teams. They identified six “infor-
mal, implicit, transient, and spontaneous” roles performed
by practitioners to reinforce the self-organizing nature of
agile practice. These roles include, for example, mentors who
guide and inform the team in using agile methods, translators
who communicate between customers and technical team, and
champions who acquire supports from senior management.
Our study builds upon these work and explores the dynamics
of various activity-based roles in OSS communities.
B. OSS Community Structure
Much work that investigated the OSS community structure
is based on the “onion” model [19], [25]. This model proposed
a layered structure of responsibilities for OSS projects that
included a small number of core members and a larger number
of peripheral developers and bug fixers [19]. Mockus et al.
[17] examined the Apache web server and the Mozilla browser
as case studies and empirically generated several hypotheses
concerning the OSS community structure. These hypotheses
echoed with the “onion” model that a small number of
developers contributes to the majority of the codebase.
Because of the self-organizing nature of OSS communities
[13], researchers have particularly investigated the evolution
of the OSS structure [6], [15], [21]. For example, Cheng et
al. [6] identified several factors that significantly influenced
developers’ evolution into a core member in OSS ecosystems;
such factors included the total number of projects developer
were willing to join and the degree to which the developer’s
peers were closely connected. Joblin et al. [15] also identified
that the OSS communities tended to evolve from a hierarchi-
cal structure to a hybrid one with a greater distribution of
contributions while the number of developers increases.
More closely related to our work, several recent studies
focused on exploring classification methods for OSS com-
munities. Through a clustering analysis on code committing
metrics extracted from ten OSS projects, Di Bella et al.
(2013) identified three major factors and four developer role
groups that fell on the spectrum from core to occasional
rare developers [10]. Agrawal et al. (2016) also adopted a
clustering approach and explored decision tree models to
classify OSS code committers; their developer classes also
ranged from core developers to less engaged developers [2].
A major limitation of these studies is that they only focused
on code committing activities. While we adopted a similar
statistical approach, our study focused on a much wider va-
riety of actions beyond code contribution and identified more
descriptive activity-oriented factors and roles. We also aimed
to extract common roles in a wide range of OSS projects.
In sum, while previous work has demonstrated non-
negligible effort on understanding the roles and their structures
in ICTs and OSS communities, there are seldom explicit
investigations, with the aim of improving tool support in OSS,
on the correlations among actions performed during goal-
driven activities, nor on the dynamics of activity migrations
accompanied by frequent role changes. Therefore, our work
fills the gap by exploring those important aspects with a data-
driven approach and by following up with a detailed discussion
on the implications for OSS tool design.
III. MET HO DS
We analyzed user action data within the last three years
from 29 GitHub projects that exhibit diverse characteristics.
All data was collected in January 2018.
A. Projects Selection
To cover a wide range of OSS communities, we focused
on projects in different application domains. Particularly, we
randomly selected one project in each category in GitHub
“Collections” 1. GitHub “Collections” are curated lists (a total
of 31 lists at the time of our data collection) of recently
active and influential projects and communities. We eliminated
two lists, “Open data” and “Policies”, which focused on non-
software projects. Table I includes the names of the selected
projects. These projects involved a total of 20,838 unique
contributors (including code contributors, issue reporters and
discussion participants, and pull request reporters and discus-
sion participants), 41,275 issues, 73,763 pull requests, and
240,024 commits. The code repositories are comprised of
4,963,540 lines of code in 24,451 files, covering 15 program-
ming languages.
B. Metrics Selection
To effectively assess the participants’ contribution to their
OSS community, we selected metrics gathered from various
aspects. Those metrics describe the detailed actions contrib-
utors take in order to participate on the OSS projects. First,
code contribution metrics include numbers of commits made,
lines of code changed, and files edited, as well as metrics
related to pull requests (PRs) made by contributors. Second,
opinion contribution metrics assess actions associated with
reporting issues and commenting in issue and PR discussions.
Third, network-related metrics include the number of times a
participant was mentioned or referred other issues or PRs in
discussions. Finally, administration metrics measure manage-
rial actions such as managing labels or manipulating issues or
PRs. Those metrics were inspired by several previous works
[2], [10], [14] and are summarized in Table II.
C. Data Collection
We aimed at extracting the necessary metrics from the
repositories of the 29 GitHub projects and focused on the con-
tributor actions within the three-year period between January
1st, 2015 and January 1st, 2018. To collect such a data set, we
1https://github.com/collections/

TABLE I
NAM ES OF GI THU B PROJ EC TS SE LE CTE D TO OU R ST UDY
accessibility-developer-tools better errors hospitalrun-frontend neovim refined-github the silver searcher
adarkroom brew jekyll picongpu SoundManager2 TrueCraft
advocacy.mozilla.org cocos2d-html5 kubernetes primer spine urh
artsy.github.io csslint madison pysc2 superpowers-core utron
basscss guardian/frontend mention-bot railsbridge/docs swipl-devel
TABLE II
ACTION METRICS TO ASSESS OSS PARTICIPANT’S CONTRIBUTION
Type Metric
Code
Contrib.
# of commits made
# of line of code changed in the codebase
# of files worked on
# of pull requests (PRs) made
Avg. length of PR descriptions*
Opinion
Contrib.
# of issues reported
Avg. length of issue descriptions*
# of comments made in issue discussions
Avg. length of issue comments*
# of comments made in PR discussions
Avg. length of PR comments*
Network
# of times being mentioned in issue comments
# of times being mentioned in PR comments
# of times referred other issues/PRs in issue comments
# of times referred other issues/PRs in PR comments
Admin.
# of times applied or removed labels on issues
# of times applied or removed labels on PRs
# of times closed issues
# of times closed pull requests
* All lengths were measured in number of characters
first used the GitHub REST API 2to download the raw data
about code committing actions, issue reporting and comment-
ing actions, PR reporting and commenting actions, as well as
issue and PR events (e.g. labels applied/removed, closed, etc.)
for each project. We then excluded any action data performed
by “bots” (i.e. automated processes presented as GitHub users
who perform event-driven actions). In order to understand the
dynamics of the OSS roles, data for each contributor was then
divided based on the quarter of a year when we calculated the
metrics. As such, our data set accumulated metrics for each
participant in each project across 12 time periods. In total, this
data set is comprised of 38,891 data points, each included 19
dimensions corresponding to the metrics described in Table II.
D. Identifying Activities and Roles
The metrics introduced previously in Section III-B were
selected to measure the concrete actions taken by the user
from distinct perspectives. Those metrics, however, might be
interrelated and can be influenced or determined by a set
of hidden factors. We hypothesize that those hidden factors
are the common activities that OSS contributors engage in
when they are serving certain roles in the projects. To identify
these activities, we first performed a Factor Analysis on the
dataset to understand and interpret the interrelations between
those metrics. Based on these factors, we then conducted a
2https://developer.github.com/v3/
Clustering Analysis to identify the prominent contributor roles.
Before the factor analysis, all metrics were standardized to
have a mean of zero and unit variance.
1) Factor Analysis: Factor analysis, especially exploratory
factor analysis, is a statistical method to discover underlying
patterns in a set of variables [8]. The main procedures for
factor analysis include factor extraction and rotation.
Maximum Likelihood and Principal Axis Factors (PAF) are
two commonly adopted factor extraction techniques [9]. We
chose the PAF approach because preliminary analysis indi-
cated that the distributions of our data violate the assumption
of multivariate normality [11]. After extracting the factors,
we used the Kaiser criterion and retained the factors with
an eigenvalue larger than 1.0, indicating that those are the
most influential factors (i.e. factors that account for the most
variance in the data) [28].
The retained factors were then rotated to attain a sim-
ple structure that supports a better interpretation. In such a
structure, each rotated factor aims to define a distinct group
of interrelated metrics. Rotation techniques can be generally
divided into orthogonal and oblique rotations; the former
produces factors that are uncorrelated while the latter allows
the factors to correlate. In social science, behaviors can rarely
be partitioned into groups that are independent [9]. We hypoth-
esized that the factors influencing the contributors’ activities
in OSS communities would also exhibit some correlations. We
therefore decided to use the oblique rotation techniques as they
would render more accurate and reproducible results when the
factors are correlated.
Factor analysis produces two results: factor loading and
factor scores. Factor loading represents the correlation of the
original metrics with each identified factor, while factor scores
are the values of each data point mapped in the factor space.
We used the factor loading result to interpret the relations
between metrics listed in Table II. The factor scores were then
used for the clustering analysis in the next step.
2) Clustering: After the activities (i.e. factors) were iden-
tified, we conducted a hierarchical clustering analysis based
on the factor scores data to identify the prominent roles of
OSS contributors. This method aims to construct a hierarchical
structure of clusters; such structure provides more information
about the dataset than unstructured clusters produced by flat
clustering methods such as K-means. Furthermore, hierarchi-
cal methods do not require a predetermined number of clusters
and most of them are deterministic. As such, this method
supports the exploratory nature of our study.
Particularly, we used an agglomerative (or bottom-up) hier-

archical clustering method. In general, agglomerative methods
first treat each data point as a singleton cluster. Pairs of
closest clusters are then successively merged until all clusters
have been merged into a single one that contains all data.
This process produces a hierarchy of clustering that can be
visualized in a tree diagram named dendrogram. Cutting the
dendrogram at a certain level creates a partition of disjoint
clusters. This step is equivalent to grouping only the clusters
with high similarity. Different strategies have been proposed
for measuring the similarity between two clusters. Based on
our initial experiment, we decided to use the ward’s method
[18]. This method produces clusters that are more compact
and suitable for identifying and interpreting prominent roles.
We used the silhouette value to measure the quality of
clusters [22]. It represents how similar one data point is to its
own cluster compared to other clusters. To choose the optimal
number of clusters, we considered the silhouette value while
also referencing to the dendrogram produced by the ward
hierarchical algorithm.
3) Interpreting activities and roles: In order to identify the
meaningful activities and roles represented in the factors and
the clusters, we followed a qualitative process that involved the
following steps. First, both authors independently examined
the actual actions represented by the influential metrics for
each factor and each wrote three to five keywords/phrases to
describe their understanding of the factor. Then the authors
discussed their notes and conducted an “Affinity Diagraming”
study to group their keywords/phrases. Next, a phrase of
higher-level abstraction was given to each group to describe
the factor. Finally, the authors discussed and agreed on the
phrase that described the biggest group in the affinity diagram
of each factor as the activity it represented. We adopted a
similar process in identifying the roles from the clustering
analysis results.
E. Analyzing Role Dynamics
To identify patterns in the dynamics of changes in roles
assumed by individual contributors, we first analyzed the
frequency of changes among the roles with respect to all
contributors. We then measured the role change intensity
(RCI) for each contributor. A contributor’s RCI was calculated
by accumulating, over the 12 time periods, the quantity of
role change between each two consecutive time periods; this
quantity is measured using the Euclidean distance between
cluster centroids of the two roles taken by the contributor
in two consecutive time periods. To accommodate the large
range of change intensity values and to ease comparison, we
calculate RCI using a logarithmic scale. Therefore, the overall
Role Change Intensity (RCI) for each contributor iis:
RoleChangeIntensity(i) = log10
12
X
t=2
dist(Ri
t,Ri
t−1)(1)
where Ri
tis the cluster centroid of the role assumed by
contributor iat time tand dist(A,B) = pPn(an−bn)2
represents the Euclidean distance between vectors Aand B.
This measure provides an ordinal evaluation of the intensity
of the contributors’ role change.
IV. RES ULT S
In the following sections, we first present our results on
factor and clustering analyses. We then present findings on
role dynamics.
A. Activity Extraction
Based on the criterion introduced in Section III-D1, we
retained six factors that had eigenvalues greater than 1.0. These
six factors explained 61% of the data variance. The factor
loading results are shown in Table III. Based on the qualitative
analysis described in Section III-E, we explain the activities
represented in these factors as follows:
−Factor 1 measures three types of actions: commenting,
being mentioned in comments, and manipulating labels
on PRs. The commenting actions may be associated with
several purposes such as voicing opinions, providing sug-
gestions, and asking or answering questions. But this factor
is most heavily influenced by the number of times the
contributor being mentioned; it also puts a heavy weight
on label manipulation actions. These facts indicated that it
mainly measures behaviors of providing information and
knowledge about the project. We thus name this activity
Knowledge Sharing.
−Factor 2 exclusively measures participants’ contributions to
the codebase. We name it Code Contribution.
−Factor 3 measures issue referring and label manipulating
actions. We found that issue referring actions are usually
associated with identifying duplicated issues or redirecting
participants to move their discussion to other issues. At
the same time, manipulating issue labels usually involve
categorizing issues (e.g. into bugs or feature requests),
identifying duplicated issues, and/or indicating stages in
issue resolving progress (e.g. triaging, assigned). We thus
name this activity Issue Coordination.
−Factor 4 is mostly associated with actions of closing issues
or PRs. We name this activity Progress Control.
−Factor 5 is influenced by actions of making PRs and
working on a large number of files. These indicate feature
tweaking or bug fixing activities in which contributors
make small changes on many files and file PRs for these
changes to be included in the main repository. We thus
name this activity Code Tweaking.
−Factor 6 is only influenced by the number of issues
reported. We thus name it Issue Reporting.
The factor analysis result also demonstrated some corre-
lations among the extracted activity dimensions (see Table
IV). Particularly, Knowledge Sharing, Issue Coordination, and
Progress Control exhibited high correlations (all pair-wise cor-
relation coefficients r > 0.5). Two other pairs of dimensions,
Knowledge Sharing–Code Tweaking and Issue Reporting–
Issue Coordination, also demonstrated moderate correlation
(r > 0.4). These results supported our hypothesis that factors

TABLE III
FACTO R LOA DI NGS O F TH E ACTI ON M ETR IC S
Metrics Factor1 Factor2 Factor3 Factor4 Factor5 Factor6 h2u2
# of commits made 0.00 1.03 0.02 -0.07 -0.04 0.05 0.997 0.003
# of line of code changed in the codebase 0.00 1.03 0.02 -0.07 -0.04 0.05 0.997 0.003
# of files worked on 0.00 0.26 -0.07 0.35 0.45 -0.17 0.575 0.425
# of pull requests (PRs) made 0.06 -0.04 -0.11 0.45 0.70 0.05 0.876 0.124
Avg. length of PR descriptions 0.05 -0.01 -0.03 -0.01 0.13 0.01 0.022 0.978
# of issues reported 0.30 0.04 0.18 0.11 0.11 0.35 0.643 0.358
Avg. length of issue descriptions -0.01 0.00 -0.03 0.00 0.02 0.16 0.024 0.976
# of comments made in issue discussions 0.52 -0.01 0.30 0.24 -0.13 0.16 0.900 0.100
Avg. length of issue comments -0.02 0.01 0.00 -0.01 0.00 0.1 0.008 0.992
# of comments made in PR discussions 0.72 -0.01 0.09 0.03 0.25 -0.12 0.820 0.180
Avg. length of PR comments 0.00 -0.01 0.04 -0.02 0.09 0.03 0.013 0.987
# of times being mentioned in issue comments 0.78 0.01 0.1 0.01 -0.02 0.14 0.840 0.160
# of times being mentioned in PR comments 1.02 0.01 -0.16 -0.2 0.2 -0.22 0.743 0.257
# of times referred other issues/PRs in issue comments -0.12 0.02 1.06 -0.07 0.02 -0.15 0.808 0.192
# of times referred other issues/PRs in PR comments 0.06 0.00 0.59 -0.05 0.21 0.00 0.503 0.497
# of times applied or removed labels on issues 0.06 0.01 0.72 0.24 -0.23 -0.07 0.725 0.275
# of times applied or removed labels on PRs 0.58 0.00 0.13 -0.03 0.15 -0.07 0.516 0.485
# of times closed issues 0.28 -0.03 0.08 0.65 -0.24 0.04 0.701 0.299
# of times closed pull requests -0.30 -0.08 0.07 0.95 0.33 -0.06 0.857 0.144
Activity Name Knwl.
Sharing
Code
Contrib.
Issue
Coord.
Prog.
Ctrl.
Code
Twking.
Issue
Rptg.
Note 1: The h2column represents the estimated proportion of variance of the each metrics that are shared with other metrics and can
explained by factors. The u2column (equals 1−h2) denotes the variance that are unique to the metric itself.
Note 2: Yellow cells indicate that the loading is greater than 0.5; green cells indicate that the loading is between 0.3 and 0.5.
TABLE IV
COR REL ATIO N COE FFIC IEN T AM ONG FAC TOR S
Knwl.
Sharing
Code
Contri.
Issue
Coord.
Prog.
Ctrl.
Code
Twking.
Code Contrib. 0.18
Issue Coord. 0.70 0.09
Progress Ctrl. 0.61 0.35 0.56
Code Twking. 0.47 0.30 0.29 0.32
Issue Rptg. 0.38 -0.05 0.44 0.13 0.22
influencing the contributors’ actions in the OSS community
are not independent.
B. Roles Identification
Figure 1 shows the dendrogram of our hierarchical cluster-
ing results. We observed that there are two major groups of
clusters that exhibited markedly different structures. The ma-
jority of the data points (N= 37,310) fell into a cluster with a
low dendrogram height, while some data points (N= 1,581)
represented a much higher height. In other words, the variance
among sub-clusters in the first group was much smaller than
that of the second group. This difference indicated that our
data included two very distinct groups of users.
By examining the cluster centers and samples from each
group, we found that the second group generates a much
higher value in all factor dimensions when compared with
the first group; in other words, contributors in this group
are much more active in terms of all activities indicated by
the factors. We thus consider the second group as comprised
of Active Contributors in their communities, while the first
group represents the Supporting Contributors. Because the
0 50 100 150 200 250 300
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Supporting Participants
Active Participants
Supporting Participants
Active Participants
Fig. 1. Hierarchical tree of clustering results. The red lines indicates the
height cutoff values for the two groups.
sub-cluster distances within these two high-level groups are
very different, we cut the two sub-trees at different heights
when identifying the specific role clusters.
Based on the silhouettes measure and the dendrogram
structure, we considered four clusters in the Active Contrib-
utors group and five clusters for Supporting Contributors;
the red lines on Figure 1 indicates the height cutoff values.
Once the clusters were determined, we followed a qualitative
process and named the clusters based on the activity space
characteristics of each cluster centroid and analysis of actual
actions performed by representative users in each cluster.
The characteristics for those clusters are shown in Figure 2
and Figure 3 respectively. We discuss those clusters and our

-0.1235191 -0.2124043 -0.2553889
Knowledge
Sharing
Code
Contribution
Issue
Coordination
Progress Control
Issue Fixing
Issue Reporting
Progress Controller
Engaged Issue Reporter
Issue Fixer
Occasional Issue Reporter
Rare Contrib utor
1.75
0.75
Knowledge
Sharing
Code
Contribution
Issue
Coordination
Progress Control
Issue Fixing
Issue Reporting
All-Rounder
Coor dinator
Core Developer
Intense Code Contributor
10
6
2
46.5
Code Tweaking
Fig. 2. Activity space characteristics of roles in the Active Contributors group.
-0.1235191 -0.2124043 -0.2553889
Knowledge
Sharing
Code
Contribution
Issue
Coordination
Progress Control
Issue Fixing
Issue Reporting
Progress Controller
Engaged Issue Reporter
Issue Fixer
Occasional Issue Reporter
Rare Contrib utor
1.75
0.75
Knowledge
Sharing
Code
Contribution
Issue
Coordination
Progress Control
Issue Fixing
Issue Reporting
All-Rounder
Coor dinator
Core Developer
Intense Code Contributor
10
6
2
46.5
Code Tweaking
Fig. 3. Activity space characteristics of roles in the Supporting Contributors
group.
rationale for naming the roles as follows.
Among the Active Contributors,Intense Code Contribu-
tors exerted an extremely high contribution to the codebase.
Additionally, there was only a small number of contributors
assumed this role. Their main focus seemed to be developing a
certain functionality of the software within a short time period.
Coordinators provided only a small amount of code contri-
bution. Instead, they focused mainly on Knowledge Sharing,
Issue Coordination, and Issue Reporting activities. They are
usually the owner of the project or a core member of the
community. Core Developer exerted very little contribution to
Issue Reporting but performed actively in Code Contribution,
Code Tweaking, Progress Control, and Knowledge Sharing.
They seemed to focus mainly on development and knowledge
sharing about the code. All-Rounders provided a medium
level of contribution in all dimensions.
The Supporting Contributors usually focused on only one
or two activities. Engaged Issue Reporters and Occasional
Issue Reporters both focused on Issue Reporting, but differed
on the quantity of their contributions. Progress Controllers
mostly engaged in the Progress Control activity, with some
contribution to Knowledge Sharing and Issue Coordination;
they almost never engaged in Code Tweaking contributions.
An analysis of sample users of this group revealed that they
are usually core members of the community and focused
on activities such as code reviewing, quality control, and
approving and merging PRs. Issue Fixers focused on making
small tweaks to the code or fixing bugs. Rare Contributors
only participated in a minuscule amount of activities.
C. Role Dynamics
Among all contributors included in our data set, most
(N= 16,706,78.9%) only assumed the Rare Contributor
role in certain periods of time during the past three years.
There were also two contributors who engaged in their projects
throughout the analyzed time periods with the same role (All-
Rounder). We excluded them in our analysis. Within the rest
of the contributors, there are 4,483 who only assumed roles
in the Supporting role group throughout the 12 time periods.
The rest (N= 479) have assumed roles in the Active role
group at least one time in the past three years. We focused
on analyzing the role change dynamics of these two types
OSS community contributors. When performing the analysis,
we considered “Absent” (i.e. did not perform any contribution
during a time period) as an additional role type.
Figure 4 shows the heatmap of role transition frequency
for contributors who only assumed the Supporting roles. Not
surprisingly, the most frequency transition happened among
Absent, Rare Contributor, and Occasional Issue Reporter roles.
The transition frequency from Absent to the other roles also
indicated ways people got involved to an OSS community:
people rarely started as a Progress Controller; aside from
occasional contributions, contributors usually began to engage
in a project by assuming Issue Fixer and Engaged Issue Re-
porter roles. Interestingly, while any transition to the Progress
Controller was rare, the transition from Progress Controller to
Occasional Issue Reporter was frequent. This may illustrate
a retiring path of community core members if they do not
continue contributing as an Active Participant.
To
From
Absen t
Rare
Contri.
Issue
Fixer
Progr ess
Controller
OCC Issue
Reporter
ENG Issue
Reporter
Absen t ⎼2048 253 33213 278
Rare Contri. 2591 ⎼194 8752 81
Issue Fix er 95 272 ⎼171 5
Progr ess C ontroller 118 3⎼511 0
OCC Issue Reporter 2248 1492 76 2⎼92
ENG Issue R eporter 166 136 16 00⎼
To
From
Absen t
Rare
Contri.
Issue
Fixer
Progr ess
Controller
OCC Issue
Reporter
ENG Issue
Reporter
Absen t ⎼2048/1587 253/250 3/3 3213/3100 278/278
Rare Contri. 2591/1738 ⎼194/163 8/5 752/ 686 81/76
Issue Fix er 95/95 272/252 ⎼1/1 71/71 5/5
Progr ess C ontroller 1/1 18/11 3/3 ⎼511/377 0/0
OCC Issue Reporter 2248/2167 1492/ 1325 76/70 2/ 2 ⎼92/82
ENG Issue R eporter 166/165 136/135 16/13 0/0 0/0 ⎼
Fig. 4. Role transition frequency heatmap for contributors who only assumed
the Supporting roles.
Figure 5 shows the heatmap of role transition frequency for
contributors who have assumed the Active roles. Aside from
transitions between Absent and Rare Contributors, the most
frequent transitions happened between All-Rounder (Active
role) and Issue Fixer (Supporting role). This type of transition
may have represented a working style of a group of OSS
contributors, who generally engaged in all aspects of the
community but switch to focus on issue fixing when issues ac-
cumulate. Transitions among All-Rounder (Active role), Rare
Contributor (Supporting role), and Occasional Issue Reporter
(Supporting role) were also frequent, indicating many active
community contributors may take breaks from their work.

To
From
Absent
All-Round er
Coordinator
Core
Developer
Intense
Code Contri.
Rare Contri.
Issue Fixer
Progr ess
Controller
OCC Issue
Reporter
ENG I ssue
Reporter
Absent ⎼108 412180 55 143 25
All-Round er 26 ⎼34 61 2109 181 32 82 30
Coordinator 132 ⎼4146412
Core Developer 044 10 ⎼125001
Intense Code Contri. 0420⎼11000
Rare Contri. 174 93 330⎼71 11 74 11
Issue Fixer 14 152 51094 ⎼455 4
Progr ess C ontroller 326 01017 8⎼5 1
OCC Issue Reporter 14 72 120109 46 4⎼23
ENG I ssue R eporter 234 03020 9 0 33 ⎼
Fig. 5. Role transition frequency heatmap for contributors who have assumed
the Active roles.
We calculated a Role Change Intensity (RCI) score for each
participant in each project using Equation 1. As the cluster dis-
tances among the Supporting roles are close to each other, the
RCI scores for contributors who only assumed the Supporting
roles are expected to be close to zero. As a result, we only
focused on RCI scores for contributors who have ever assumed
the Active roles. Figure 6 shows the histogram of their RCI
scores. The results showed a right-skewed distribution with a
median of 0.99 (IQR = 1.21 −0.92). Examining the scenario
in which only one role change has occurred throughout the
whole time periods, we found that the median RCI across all
types of role changes is 1.11 (IQR = 1.26 −0.35). These
results indicated that most contributors engaged in a medium-
level RCI while some experienced role changes across a
medium to high-level intensity.
Histogram of data
data
Frequency
0.5 1.0 1.5 2.0
0 50 100 150
Fig. 6. Histogram of RCI across contributors who have assumed the Active
roles.
V. DISCUSSION
Our work provides several implications for designing OSS
tools to support role-based interactions. In this section, we first
discuss these implications. We then consider the limitations of
our current study and discuss directions for future work.
A. Mediate OSS Activities Instead of Actions
Current OSS tools usually involve features that focus on
supporting low-level actions such as code committing, issue
reporting, commenting, applying labels, etc. There is a lack of
focus on mediating higher-level OSS activities. Through the
factor analysis, we identified six activities that most clearly
distinguished the roles of OSS contributors. Some of them,
such as Code Contribution and Issue Reporting, only involved
a small number of actions and were well supported in the
current tools. However, others involved multiple actions that
were currently supported in different, and sometimes isolated
tool features. For example, the Issue Coordination activity
involves actions to create links among the issues and the pull
requests, as well as managing issue labels; on GitHub, there is
no connection between the link creation (through commenting)
and the issue labeling features.
Reflecting on the Activity Theory, tools need to serve as
“functional organs” to help users achieve their goal-oriented
activities [16], [20]. We argue that the OSS tool designers need
to consider the activities identified in this paper, which were
aligned with the representative goals that OSS contributors
hold when performing the corresponding actions. Particularly,
they may explore connections surrounding the features that
support the underlying actions for each activity to facilitate
a smooth transition among the actions. Moreover, based on
the correlations found among the activities, OSS tool design-
ers may consider more sophisticated feature connections to
support users move among activities.
B. Support Role-Based Interaction
Through the clustering analysis, we identified four Active
roles and five Supporting roles of OSS contributors. While
the literature has strongly advocated role-based interaction
in software engineering tools [26], the realization of such
interaction is still immature in the OSS world. One reason for
this gap is that there is currently little knowledge or guidance
for the tool designers to have a clear conception as to what
high-level activities and detailed actions each role takes. Our
data-driven and activity-based roles addressed this limitation.
On one hand, the roles identified in this paper reflected some
characteristics of the roles in the literature (e.g. the “onion”
model [19]). For example, confirming the hypothesis posed
in the “onion” model, our data indicated a small number of
Active contributors who make a large amount of contributions
and a vast number of Supporting contributors. On the other
hand, however, our roles provided a non-simplistic trace to the
main activities each role focuses on. For example, our results
showed that the Progress Controllers do not only perform the
Progress Control activity but they were usually also involved
in Knowledge Sharing and Issue Coordination; the Engaged
Issue Reporters usually also perform the Issue Coordination
activity. As a result, these roles paint a more comprehensive
picture about activities and responsibilities of OSS contribu-
tors. The OSS tool designers can use this information to better
satisfy the goals and needs of OSS contributors in role-based
interaction design. Particularly, they can use the activities and
the actions underlying each role as a design guideline.
C. Support Role Change: Onboarding and Retiring
There is limited discussion about OSS tools that support role
change in the literature. However, our data indicated that role
change in OSS communities is both frequent and somewhat
intense. As a result, techniques and tools that facilitate a
smooth change of roles can be useful for OSS contributors.
While our results have indicated a complex role change
model, onboarding and retiring are among the most important

types of role change for OSS communities. Our data confirmed
a common impression that OSS contributors usually get in-
volved in a project through issue reporting and fixing. We also
identified that a common retiring path of Active contributors
is also though issue-related activities. These findings indicated
a central role of the Issue Management Systems in the on-
boarding and retiring processes. Tool designers may consider
including features in the Issue Management Systems to support
new contributors to be better engaged in the community culture
and acquire the necessary knowledge and skill. They may
also enhance the Issue Management Systems to help retiring
members transfer knowledge and tasks.
D. Limitations and Future Work
Although diverse, the contribution metrics used in our
study are based only on quantity, rather than quality, of the
actions taken by OSS contributors. Our research can thus
be extended with studies focused on extracting qualitative
measures of contribution. Additionally, while the 29 OSS
projects analyzed in this work were carefully selected to cover
a wide variety in terms of application domains, programming
language, community size, and code base size, future work
that validates our findings in a larger amount of OSS projects
and communities can be useful. Moreover, we focused on in-
vestigating OSS contributors’ roles within a project. However,
many contemporary OSS communities were structured around
a group of projects (i.e. a project ecosystem). Exploring how
our model and method can generalize to such higher-scaled
OSS communities is an interesting future work.
VI. CONCLUSION
In this study, we adopted a data-driven approach to under-
standing the diverse roles and their dynamics in OSS commu-
nities. From an analysis of 29 OSS projects, we extracted six
activities that determined four Active roles and five Supporting
roles. This approach allowed us to provide rich informa-
tion, grounded in the data, about the actions and activities
performed by each role. Through the lens of the Activity
Theory, such information rendered useful design guidelines
for role-based OSS tools. We argue that such methodology
and the generated information are crucial to understanding and
supporting the collaboration among diverse OSS contributors.
REFERENCES
[1] S. T. Acu˜
na and N. Juristo. Assigning people to roles in software
projects. Software: Practice and Experience, 34(7):675–696, jun 2004.
[2] K. Agrawal, M. Aschauer, T. Thonhofer, S. Bala, A. Rogge-Solti, and
N. Tomsich. Resource Classification from Version Control System
Logs. In 2016 IEEE 20th International Enterprise Distributed Object
Computing Workshop (EDOCW), pages 1–10. IEEE, sep 2016.
[3] O. Arazy, J. Daxenberger, H. Lifshitz-Assaf, O. Nov, and I. Gurevych.
Turbulent Stability of Emergent Roles: The Dualistic Nature of Self-
Organizing Knowledge Coproduction. Information Systems Research,
27(4):792–812, dec 2016.
[4] J. B. Barlow. Emergent roles in decision-making tasks using group
chat. In Proceedings of the 2013 conference on Computer supported
cooperative work - CSCW ’13, page 1505, New York, New York, USA,
2013. ACM Press.
[5] A. Ben Fadhel, D. Bianculli, and L. C. Briand. Model-driven run-time
enforcement of complex role-based access control policies. In Proceed-
ings of the 33rd ACM/IEEE International Conference on Automated
Software Engineering - ASE 2018, pages 248–258, New York, New
York, USA, 2018. ACM Press.
[6] C. Cheng, B. Li, Z.-Y. Li, Y.-Q. Zhao, and F.-L. Liao. Developer Role
Evolution in Open Source Software Ecosystem: An Explanatory Study
on GNOME. J. Comput. Sci. Technol., 32(2):396–414, mar 2017.
[7] J. Cheng and J. L. Guo. How do the open source communities address
usability and ux issues: An exploratory study. In Extended Abstracts
of the 2018 CHI Conference on Human Factors in Computing Systems,
CHI EA ’18, New York, NY, USA, 2018. ACM.
[8] D. Child. The essentials of factor analysis. A&C Black, 2006.
[9] A. B. Costello and J. W. Osborne. Best practices in exploratory factor
analysis: Four recommendations for getting the most from your analysis.
Practical assessment, research & evaluation, 10(7):1–9, 2005.
[10] E. di Bella, A. Sillitti, and G. Succi. A multivariate classification of
open source developers. Information Sciences, 221:72–83, feb 2013.
[11] L. R. Fabrigar, D. T. Wegener, R. C. MacCallum, and E. J. Strahan.
Evaluating the use of exploratory factor analysis in psychological
research. Psychological methods, 4(3):272, 1999.
[12] GitHub. How to contribute to open source. https://opensource.guide/,
2019.
[13] R. Hoda, J. Noble, and S. Marshall. Self-Organizing Roles on Agile
Software Development Teams. IEEE Transactions on Software Engi-
neering, 39(3):422–444, mar 2013.
[14] M. Joblin, S. Apel, C. Hunsen, and W. Mauerer. Classifying Developers
into Core and Peripheral: An Empirical Study on Count and Network
Metrics. In Proceedings of the 39th International Conference on
Software Engineering, pages 164–174. IEEE, may 2017.
[15] M. Joblin, S. Apel, and W. Mauerer. Evolutionary trends of developer
coordination: a network approach. Empirical Software Engineering,
22(4):2050–2094, Aug 2017.
[16] V. Kaptelinin. Activity Theory: Implications for Human- Computer
Interaction. In Context and consciousness: Activity theory and human-
computer interaction, pages 103–116. MIT, 1996.
[17] A. Mockus, R. T. Fielding, and J. D. Herbsleb. Two case studies of
open source software development: Apache and Mozilla. ACM Trans.
Softw. Eng. Methodol., 11(3):309–346, jul 2002.
[18] F. Murtagh and P. Legendre. Ward’s hierarchical agglomerative cluster-
ing method: Which algorithms implement ward’s criterion? Journal of
Classification, 31(3):274–295, Oct 2014.
[19] K. Nakakoji, Y. Yamamoto, Y. Nishinaka, K. Kishida, and Y. Ye.
Evolution patterns of open-source software systems and communities.
In Proceedings of the International Workshop on Principles of Software
Evolution, page 76, New York, New York, USA, 2002. ACM Press.
[20] B. A. Nardi. Activity Theory and Human-Computer Interaction. In Con-
text and consciousness: Activity theory and human-computer interaction,
pages 7–16. MIT, 1996.
[21] S. Onoue, H. Hata, and K. Matsumoto. Software population pyramids:
The current and the future of oss development communities. In Pro-
ceedings of the 8th ACM/IEEE International Symposium on Empirical
Software Engineering and Measurement, ESEM ’14, pages 34:1–34:4,
New York, NY, USA, 2014. ACM.
[22] P. J. Rousseeuw. Silhouettes: a graphical aid to the interpretation and
validation of cluster analysis. Journal of computational and applied
mathematics, 20:53–65, 1987.
[23] J. E. Tomakyo and O. Hazaan. Human Aspects of Software Engineering.
Laxmi Publications, 2005.
[24] L. S. Vygotsky. Mind in Society: Development of Higher Psychological
Processes. Harvard University Press, 1981.
[25] Y. Ye and K. Kishida. Toward an understanding of the motivation open
source software developers. In Proceedings of the 25th International
Conference on Software Engineering, ICSE ’03, pages 419–429, Wash-
ington, DC, USA, 2003. IEEE Computer Society.
[26] H. Zhu, M. Zhou, and M. Hou. Support Collaboration with Roles. In
Contemporary Issues in Systems Science and Engineering, pages 575–
598. John Wiley & Sons, Inc., Hoboken, NJ, USA, apr 2015.
[27] H. Zhu, M. Zhou, and P. Seguin. Supporting Software Development
With Roles. IEEE Transactions on Systems, Man, and Cybernetics -
Part A: Systems and Humans, 36(6):1110–1123, nov 2006.
[28] W. R. Zwick and W. F. Velicer. Comparison of five rules for determining
the number of components to retain. Psychological bulletin, 99(3):432,
1986.