=Paper=
{{Paper
|id=Vol-3220/keynote
|storemode=property
|title=OpenCitations: a short introduction (keynote)
|pdfUrl=https://ceur-ws.org/Vol-3220/keynote.pdf
|volume=Vol-3220
|authors=Silvio Peroni
|dblpUrl=https://dblp.org/rec/conf/jcdl/Peroni22
}}
==OpenCitations: a short introduction (keynote)==
https://ceur-ws.org/Vol-3220/keynote.pdf
OpenCitations: a short introduction
Silvio Peroni1,2
1
Research Centre for Open Scholarly Metadata, Department of Classical Philology and Italian Studies, University of
Bologna, Bologna, Italy
2
Digital Humanities Advanced Research Centre (/DH.arc), Department of Classical Philology and Italian Studies,
University of Bologna, Bologna, Italy
Abstract
In this paper, I introduce a brief history of open citations, their main characteristics and use in the
context of OpenCitations, a scholarly infrastructure organisation dedicated to open scholarship and the
publication of open bibliographic and citation data using Semantic Web technologies.
Keywords
OpenCitations, open citation data, open bibliographic metadata, Semantic Web
1. The origins of open citations
The concept of open citations [1] is strongly tied with that of the Web. Since 1989, the Web
has drastically changed how we think about academic publishing and science. Publishers have
adopted Web Standards to create and deliver their products quickly and to a broader audience.
Standards, guidelines, and services based on Web technologies have been proposed in the past
30 years to increase the discoverability of academic products and publications, improve research
practices and allow reusability of scholarly data in different applicative contexts. Open citations
are no exception.
Even if the definition of open citations has been introduced recently, past works implicitly
started to highlight their main characteristics. As far as I know, the first embryonal description
of open citations is in Robert Cameron’s visionary article published in 1997 [2]. In this article,
he speculated about the existence of a decentralised and freely available Universal Citation
Database. Such a database would have had daily updates and links to every scholarly work,
providing information for all types of publications (from journal articles to technical reports,
datasets, and other publication types) and being equally visible and accessible to all.
From this initial Web age, things have started to develop. In the same year of Cameron’s
article, CiteSeer was established [3], a service that crawled citations from PostScript documents
available on the Web. Along the same lines, a few years later, CiteBase was created in the context
of the OpCit project [4]. In 2004, Google Scholar (https://scholar.google.com) was launched to
provide one of the first open Web interfaces for looking at a scientist’s paper and the citations
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that this paper received (even if the data are not openly accessible). A few years later, CiteSeerX
[5] was proposed as an evolution to CiteSeer to address some problems of its predecessor.
However, the tipping point for open citations was when, in 2009, David Shotton in-
troduced the concept of semantic publishing [6], which concerns the use of Semantic
Web technologies applied to the scholarly publishing domain to make journal articles
and other scholarly publications more discoverable and reusable. This idea led him to
the JISC OpenCitations project in 2010 (https://opencitations.wordpress.com/2010/07/15/
jisc-open-citations-aims-objectives-and-final-outputs/), a year-long project (with a subsequent
extension) that aimed at creating the first corpus of open citation data entirely available on the
Web by using URLs to identify resources and RDF to expose these data to the public.
The idea of providing open citations was spread to the scholarly and publishing community
in the following years in two different editions of the Annual Conference of Open Access
Publishers (OASPA, https://oaspa.org/conference/). Both David Shotton’s talk at OASPA 2013
and Dario Taraborelli’s speech at OASPA 2016 highlighted the essential need to release citation
data as soon as possible for the whole scholarly community.
Since 2016, everything has started to change on a large scale. The importance of open ci-
tations got a broader audience and led to the introduction of OpenCitations [7] and WikiCite
as testimonials of communities providing open citation data and services to allow their pro-
grammatic access. After these first technical implementations, in 2017, the Initiative for Open
Citations (I4OC, https://i4oc.org) was launched to convince publishers to make their reference
lists free and openly available on Crossref (https://crossref.org) [8]. In the following years,
other international events and scholarly initiatives helped increase the interest in open citations
and related technical infrastructures. The successful movement toward public domain citation
data is now more strong than ever and “improve the transparency and robustness of scientific
portfolio analysis, improve science policy decision-making, stimulate downstream commercial
activity, and increase the discoverability of scientific articles” [9].
2. What is an open citation
In the previous section, I used the concept of open citations several times. However, I have
not clarified what it is about and the characteristics a citation must have to be claimed as open.
However, first, it is necessary to explain what I refer to when I mention the word citation.
A bibliographic citation is a conceptual directional link from a citing entity to a cited entity
to acknowledge or ascribe credit for the contribution made by the authors of the cited entity.
This link is defined using particular textual devices such as a bibliographic reference in the
reference list, denoted by an in-text reference pointer – e.g. “[3]” or “(Doe et al., 2013)” – within
the body of the citing entity.
The citation data related to a particular citation must include the representation of such
a conceptual directional link and the basic metadata of the citing entity and the cited entity,
i.e. sufficient information to create or retrieve textual bibliographic references for each of the
entities involved in the citation (i.e. the citing entity and the cited entity).
A bibliographic citation is an open citation when the data needed to define the citation are
compliant with the following principles [10]:
Figure 1: The five principles citation data must comply with to talk about an open citation.
• structured – citation data must be expressed in one or more machine-readable formats
such as JSON or RDF;
• separate – citation data must be available without the need to access the source bibli-
ographic entity (e.g. the article or book) in which the citation is defined, which can be
even behind a paywall;
• open – citation data must be freely accessible and reusable without restrictions, for
example, by publication under the CC0 1.0 Universal waiver/license;
• identifiable and available – citing and cited entities must be identified by using a
specific persistent identifier scheme (e.g. a DOI) or a URL. In addition, by resolving the
identifiers of the citing and cited entities, it must be possible to obtain the basic metadata
of both entities, sufficient to create or retrieve textual bibliographic references for each of
them. Such basic entity metadata must also be structured, separate and open.
These principles have been thoroughly followed in the technical developments of OpenCita-
tions, introduced in the following section.
3. OpenCitations, a scholarly infrastructure organisation
OpenCitations (https://opencitations.net) [7], of which I am proudly one of its directors, is a
scholarly infrastructure organisation dedicated to open scholarship and the publication of open
bibliographic and citation data using Semantic Web technologies. We also undertake advocacy
for open scholarly metadata, mainly via the Initiative for Open Citations (I4OC, https://i4oc.org)
and the Initiative for Open Abstracts (I4OA, https://i4oa.org). Our goal is to provide open
metadata with a scope, depth, accuracy and provenance surpassing commercial sources.
We provide the OpenCitations Data Model [11] that we use to describe all the bibliographic
metadata and citation data OpenCitations provides. Of course, we also provide bibliographic and
citation data (all released using the CC0 waiver to maximise their reuse), available in different
collections, including the OpenCitations Indexes, our primary collection. In addition, all the
software we developed to gather and expose these data is available in our GitHub repository
(https://github.com/opencitations) and released with open source licenses. Finally, all the
data are available online: full dumps of OpenCitations data can be downloaded and accessed
programmatically via REST APIs, SPARQL endpoints, and other Web interfaces.
Our primary database, COCI (the OpenCitations Index of Crossref open DOI-to-DOI citations)
[12], currently hosts more than 1.29 billion citations. All these citations have been made available
in Linked Open Data. They can be accessed programmatically using our REST API by specifying
either publication’ DOI or the Open Citation Identifier (OCI) [13] identifying the complete
citation, i.e. the relation entity A cites entity B.
Since 2020, OpenCitations has significantly benefited from crowdfunding from the scholarly
community, which has resulted from (a) the Global Sustainability Coalition for Open Science
Services’s (SCOSS, https://scoss.org) selection of OpenCitations as a scholarly infrastructure
worthy of support, and (b) its involvement in international projects, such as the OpenAIRE-
Nexus project (https://www.openaire.eu/openaire-nexus-project) and RISIS project (https://
www.risis2.eu/).
OpenCitations espouses the UNESCO principles of Open Science [14], the Principle of Open
Scholarly Infrastructures [15], the FAIR data principles that data should be Findable, Accessible,
Interoperable, and Reusable [16], and the I4OC principles that citation data should be Struc-
tured, Separable, and Open (https://i4oc.org/#goals). In compliance with these values, one of
OpenCitations’ main priorities is to keep its services, software, and data always without charge
under open licenses (CC0 for data and ISC for software) to foster their maximum reuse.
4. Conclusions and future directions
This undeniable aspect of keeping all OpenCitations data and services free leads to an acknowl-
edged sustainability issue, principally in terms of salaries and technical infrastructure costs.
OpenCitations can rely on an international network of generous supporters that apply for
membership and donation programmes. We are grateful to the institutions that believe in our
mission and values. However, we are already far from being a fully financially sustained infras-
tructure, and we still need help from the global scholarly community to keep open bibliographic
and citation data and related services available for many years and to reach the following goals:
• to provide high-quality metadata with full provenance relating to scholarly publications
and the citations that link them, including those in areas such as the humanities and
social sciences, the global south, and non-English publications;
• to expand our coverage into the ‘grey literature’ of reports, patents, datasets, software,
etc.;
• to surpass in terms of coverage and quality – and thereby provide an open and free
alternative to – the major commercial citation indexes;
• to provide the open data crucial for research in bibliometrics and scientometrics, and the
creation of transparent and reproducible metrics for research assessment;
• to continue developing and making public free and open-source software (FOSS) with
relevant functionality and our open services built over our data.
We (scholars, institutions, founders, etc.) can make a difference and create an open, inclusive
future for science and research. OpenCitations is a plural: together, we are OpenCitations.
Acknowledgments
I want to thank David Shotton and Chiara Di Giambattista, who provided insightful discussions,
materials and feedback which has been included in this paper, and all the people working for and
supporting OpenCitations. This work has been funded by the European Union’s Horizon 2020
research and innovation program under grant agreement No 101017452 (OpenAIRE-Nexus).
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