Towards Semantically Structuring GitHub
Dennis Oliver Kubitza1,2 , Matthias Böckmann1,2 , and Damien Graux2,3
1
University of Bonn – Germany
2
Enterprise Information Systems, Fraunhofer IAIS – Germany
3
ADAPT Centre, Trinity College of Dublin – Ireland
dennis.oliver.kubitza|matthias.boeckmann|damien.graux@iais.fraunhofer.de
Abstract. With the recent increase of open-source projects, tools have
emerged to enable developers collaborating. Among these, git has re-
ceived lots of attention and various on-line platforms have been created
around this tool, hosting millions of projects. Recently, some of these
platforms opened APIs to allow users questioning their public databases
of open-source projects. Despite of the common protocol core, there are
for now no common structures someone could use to link those sources of
information. To tackle this, we propose the SemanGit ontology, the first
ontology dedicated to the git protocol, which also describes GitHub’s
features to show how it is extensible to encompass more git-based data
sources.
1 Introduction
Open-Source technology is, once accepted as beneficial, subject to improvement
attempts under the premises of commercial marketing, ideological beliefs or just
feasibility of implementation. One of the most popular examples is Linux, with
its variety of ecosystems, ranging from commercial server distribution to open-
source desktop implementations. While not considered as heterogeneous in its
implementations, for now, the git protocol [10] faces the same development.
Developed in 2005 as a distributed version-control system, git [10] is tracking
changes in a file system while providing several properties such as data integrity
or support for distributed and non-linear workflows. Since the file system rep-
resented by git can be distributed, developers embed their changes into a local
git repository and later “push” their contributions to an online repository so
that collaborators can then have access to their modifications and contributions.
Quickly, the git protocol has evolved to provide more and more features dedi-
cated to large open-source communities and projects. In recent years, more and
more platforms emerged using the git protocol to provide their users with a
version-control system, with every one of them using additional features to pro-
vide a better user experience, faster distribution or improved maintainability.
Nowadays, GitHub seems to be the most popular platform [1] for the external
usage of git, but other providers like GitLab achieve more and more popular-
ity [1,2]. As all these systems share a common infrastructure, based on git and
principles adopted from social networks, it is possible to agglomerate the dif-
ferent approaches in a unified model and to merge these providers’ data into a
Copyright c 2019 for this paper by its authors. Use permitted under Creative Commons License
Attribution 4.0 International (CC BY 4.0).
2 Dennis Oliver Kubitza, Matthias Böckmann, and Damien Graux
common source of information. In this study, we present the SemanGit ontology,
an OWL ontology serving three goals. First, it structures data provided by the
git protocol. Second, it models as much information as possible from GitHub.
Third, it contains enough abstraction such that similar information from other
sources like BitBucket, CloudForge, GitLab, Launchpad can have a consistent
representation, using the same parental classes.
The SemanGit ontology can then be used to collect data about developers from
different domains, interlinking information about publicly available software, its
developers and interactions between them with social media and research plat-
forms. While we propose not the first ontology related to data from git [6], our
approach is a novelty, focusing on the possibilities of automated data extrac-
tion and analysis. Indeed De Nies et al. proposed the git2PROV system, tailored
to the task of extracting provenance information [6] as a feature for developers
publishing their work.
More generally, we fall within the domain of structuring public data (see
e.g. [7] focusing on describing projects). So far, numerous projects are already
providing such datasets with each one tackling a distinct domain. Among this
list, we can mention DBpedia [3] which proposes a linked version of Wikipedia,
or also LinkedGeoData [4] which deals with geographical data. Both are excellent
targets for a future interlinking of data extracted from git hosters, to enrich the
information about users origin.
2 A git Ontology and its GitHub Extension
The git protocol relies on so-called repositories for storing files and tracking
data modifications. A large share of online git repository providers add features
of their own that are not part of the git protocol, such as social features. To
create an extensible ontology, we need to implement a strict distinction between
what is part of the git protocol and what is provider specific. As an example,
according to the git protocol, the author of a commit is a pair “Name ”
whereas on GitHub an author, i.e. a user, is much more complex. It has additional
attributes such as a creation date, an avatar, a location and even social-featured
ones such as e.g. an associated website. The part of the SemanGit ontology cover-
ing the git protocol features only the data that strictly belongs to the protocol.
The classes in this section mostly form the basis from which platform-specific
classes inherit, see Figure 1 for an example. This protocol-related part is rather
small and comprises of merely four classes: users, projects (i.e. repositories),
commits and pull requests, the user class storing only an email address. The
projects refer to a URL, a time stamp of its creation and the commits that were
submitted to it. The other two classes are slightly more complex as commits have
a hierarchical structure in themselves and pull requests are requests to accept
a cross-branch commit, possibly coming from another project. Seeing that all
extensions of the git protocol are still required to provide the base functional-
ity, we have chosen a hierarchical approach for the SemanGit ontology, letting
extensions inherit from protocol-conform classes all properties they are expected
Towards Semantically Structuring GitHub 3
user Literal
string
integer
user email
string
dateTime
github user lng
Literal string
Subclass of dateTime
comment author Literal github userid github user country code
github user created at github company string github issue event created at
github user city string
github user location
boolean github issue event action
Literal
github user state github issue...
commit commited by github user deleted github issue event action specific sha
commit author github user lat
github issue event actor
string
string github login
github user github issue event for
comment
github issue assignee
github user is org
github issue reporter github issue github issue created at dateTime
string boolean github user fake
comment pos github issue id
comment for
boolean Subclass of
commit sha comment line comment created at integer
integer
comment body github project joining user
commit has parent commentable
github follower Subclass of
commit integer dateTime
commit created at Subclass of
string
Subclass of
dateTime github issue label used by
github has owner
commit message
github commit github issue project github projec...
github project join event created at
dateTime
followable
github follows
github follow...
string github issue pull request
repository has commit
Subclass of
github project joined
Subclass of
github repo ...
github user or project
Fig. 1. An excerpt of the SemanGit ontology. In this example the layers of the ontology github following since
github repo label project
are represented in three shades of blue, representing from dark to light, the git, the repository
Subclass of
github project
github project name
string
abstraction and the GitHub specific classes. dateTime
boolean
github project description
github project language repo
github pull r... github project id
repository url string
to have. The SemanGit ontology comprises three different and distinct layers of repository created at
repository langugage
githubfrom
github forked project deleted
github project has milestone github repo label name
abstraction: integer
github projec...
github project langu
1. A set of classes corresponding to entities and relations directly specified by dateTime
string
github pullgithub
request
github pull request id
pullintra branch
request merged
boolean
github project lan
the git protocol, containing the semantic representation of all information github projec... github
github pull request action pull request
delivered by the execution of this protocol. Thing
integer
github project milestone name
2. An intermediate layer abstracting any common functionality provided by boolean boolean
Datatype
(external)
different implementations of the protocol, forming the link between the git string
standards and the providers’ systems. Some of these functionalities are con-
cerning purely social relations, such as one user following another, or multiple github pull r...
github pull request action type
github pull request action id
users forming an organization.
3. Provider specific classes that usually derive from the upper layers as sub- github pull request action created at
classes and contain unique implementation features for the respective git im-
plementations. We set apart these classes corresponding to provider-specific dateTime
extensions of the protocol from the original one by adding a prefix e.g.
“github ” to the class name and their properties.
While for now being tailored to model information provided by GitHub, this
structure leaves space for any extension by other providers’ specific implementa-
tions and even encourages representations of project migration from one provider
to other alternatives.
3 Conclusion
In this study, we presented the SemanGit ontology, an ontology dedicated to
the git protocol. In addition, we also described how it can be extended to en-
4 Dennis Oliver Kubitza, Matthias Böckmann, and Damien Graux
compass additional features from public open-source platforms by considering
GitHub. The full SemanGit ontology is publicly available for further community
driven development on GitHub 1 and on our website2 . An interactive visualization
can be found on VisualDataWeb 3 . While focusing on the structure and features
of GitHub for the moment, we designed our ontology to be extensible by the
information generated by any other host of git based version-control systems.
We created this ontology as a starting point to build semantic datasets from
various collaborative-platforms. Moreover, we already built one from GitHub:
the SemanGit dataset [8]. Such datasets could then allow innovative perspec-
tives for data analysis if one considers an enrichment of data from other sources
like DBpedia [3], LinkedIn [9] or linking researchers code development with
ScienceGRAPH [5]. While the SemanGit ontology is currently published at our
homepage, we strive for the integration on external hubs such as LOV [11] in
the near future.
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accessed: August 28, 2019
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1
https://github.com/SemanGit/SemanGit/blob/master/Documentation/ontology/
2
http://www.semangit.de/
3
http://visualdataweb.de/webvowl/#opts=doc=0;editorMode=true;#iri=https://raw.
githubusercontent.com/SemanGit/SemanGit/master/Documentation/ontology/semangitontology.ttl