We’re now proud to announce the September 2021 release of COCI, which is based on open references to works with DOIs within the Crossref dump dated August 2021. This new release extends COCI with more than 92 Million additional citations, giving a total number of more than 1.18 Billion DOI-to-DOI citation links.
This latest release includes citations from the most recent articles published by the American Chemical Society, whose bibliographic references were opened in February 2021. The ACS back number citations will be available in the next COCI release, when a new processing of all the Crossref data will be completed.
Ivan Heibi, Silvio Peroni & David Shotton (2019). Software review: COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations. Scientometrics, 121 (2): 1213-1228. DOI: https://doi.org/10.1007/s11192-019-03217-6
Finally, just a reminder that the bibliographic and citation data in COCI:
can be queried using the OpenCitations Indexes SPARQL endpoint;
Now that OpenCitations is hosting over one billion freely available scholarly bibliographic citations, this is perhaps an opportune moment to look back to the start of this initiative. A little over eleven years ago, on 24 April 2010, I spoke at the Open Knowledge Foundation Conference, OKCon2010, in London, on the topic
OpenCitations: Publishing Bibliographic Citations as Linked Open Data
I reported that, earlier that same week, I had applied to Jisc for a one-year grant to fund the OpenCitations Project (opencitations.net). Jisc (at that time ‘The JISC’, the Joint Information Systems Committee) was tasked by the UK government, among other things, to support research and development in information technology for the benefit of the academic community.
The purpose of that original OpenCitations R&D project was to develop a prototype in which we:
harvested citations from the open access biomedical literature in PubMed Central;
described and linked them using CiTO, the Citation Typing Ontology [1];
encoded and organized them in an RDF triplestore; and
published them as Linked Open Data in the OpenCitations Corpus (OCC).
I told those at the conference that in this demonstration project, with limited JISC funding, we could not hope to “boil the whole ocean”, but that nevertheless there would be substantial benefits from even partial coverage of citation data from the scholarly literature:
We could show the way and establish best practice.
Despite partial coverage, all key papers would most likely be cited several times.
The overall topological structure of the citation network would be revealed.
We would create a ‘benchmark’ corpus of high-quality RDF citation data that could be used to develop analytical and visualization tools.
We could show the value of open citation data in helping scholars to discover full text articles of all types, and thus encourage subscription-access publishers to release their reference metadata.
The important thing, I said, was to make a start!
The Jisc OpenCitations Project
That JISC grant application was funded, and the project, to last for a year with modest funding of £100K, started in my lab in the Department of Zoology at Oxford University on 1st June 2010, and was subsequently extended for a further six months.
Using data from the Open Access subset of PubMed Central, we created the first prototype release of the OpenCitations Corpus of linked bibliographic citation data, containing 6,529,815 independent bibliographic records of both citing and cited entities, comprising references to ~20% of all post-1980 articles recorded in PubMed, including those to all the most important highly cited papers in every field of biomedical endeavour.
This achievement was almost entirely the result of the excellent work by our chief data wrangler Alex Dutton, whose skill and natural feel for linked data did wonders for this project. Ben O’Steen, Graham Klyne and Alistair Miles made important contributions.
The project also resulted in many other development, described here, most which were developed or at least initiated during a short but wonderfully productive collaboration with Silvio Peroni, who spent six months with me in 2010 as a doctoral student intern from the University of Bologna, to which he subsequently returned to complete his thesis and develop his academic career.
These included:
the deconstruction and re-development of the original version of CiTO into a suite of orthogonal and complementary ontologies covering the whole domain of scholarly publishing – the SPAR (Semantic Publishing and Referencing) Ontologies [2, 3];
the mapping of various existing metadata schemas into RDF using SPAR, including the DataCite Metadata Schema, and subsequently JATS, now the default NISO standard for XML markup of scholarly documents) [4]; and
After the Jisc funding ended and I, after a long career in biological teaching and research, formally retired from the Department of Zoology at the Oxford University, members of the initial OpenCitations team moved on to other things. Like so many grant-funded academic project whose initial financial support had dried up, OpenCitations could have foundered at that stage, as an interesting prototype but with too little content to be useful. However, the concept of providing an open alternative to proprietary citation indexes was too important to abandon. But how could it be transitioned into something enduring and useful, particularly when as a matter of principle one had decided that the citation data should be made freely available, thus precluding income generation by charging for ‘premium’ services or the formation of a commercial spin-off?
Finally, I realized that something radical needed to be done to move OpenCitations forward. I had maintained a lively collaboration with Silvio Peroni at the University of Bologna, resulting between 2011 and 2014 in the publication of 18 articles and conference papers concerning the SPAR ontologies, ontology development, documentation and visualization, and related topics, and in 2015 I invited him to start working with me directly on OpenCitations. It was the best decision I could have made. We decided to take the initial concept and re-implement it from the bottom up. OpenCitations gave Silvio a major computer science project to which he could apply his considerable talent, and soon resulted in the development of a revised RDF data model for describing citation data, the OpenCitations Data Model (OCDM) [5] and a suite of new software tools to harvest, organise and publish citations at linked open data [6]. The credit for almost all the subsequent conceptual and technical developments within OpenCitations, which have incrementally led to our present situation, is due to Silvio Peroni, and the scholarly community is indebted to him for the intelligence, skill and diligent application he has given to OpenCitations over the past six years. I am truly honoured to have Silvio as co-Director of OpenCitations, and wish to take this opportunity to acknowledge his contributions and to thank him publicly.
Our work on OpenCitations at that stage, summarized in [7], would not have been possible without the enthusiastic support of Silvio’s senior colleague Fabio Vitali and of the Department of Computer Science and Engineering at the University of Bologna, which not only provided a stimulating environment for Silvio’s post-doctoral work, but also supplied computing services and infrastructure at no charge to OpenCitations. It was also greatly helped by Professor David De Roure of Oxford University, who gave me an academic home and a formal affiliation within the Oxford e-Research Centre after my retirement from the Department of Zoology, which enabled me to continue to hold research grants.
As has been documented in earlier posts in this blog, we greatly benefitted in 2017 from a grant from the Alfred P. Sloan Foundation which enabled us to purchase a new and more powerful computing infrastructure for the sole use of OpenCitations and to extend and improve our software, and subsequently in 2019 by a project grant from the Wellcome Trust to develop the Open Biomedical Citations in Context Corpus, that permitted the extension of OCDM and SPAR for the characterization of in-text references and their textual contexts.
A significant breakthrough came in January 2018 with our decision to treat citations as first-class data entities, each with its own persistent identifier (PID), the Open Citations Identifier (OCI) [8]. This gave Silvio the freedom to envision a new kind of database, a citation index in which each citation had its own metadata, including citation timespan, citation categorization (e.g. self-citation), and of course the DOIs of the citing and cited publications. The creation of this new index was possible only with the incredible effort by Ivan Heibi, who served as a Research Fellow in the project funded by the Alfred P. Sloan Foundation at that time, and who was entirely responsible for developing the first version of the code necessary for creating such a database. Having harvested all the open references from Crossref metadata dumps, Silvio and Ivan created COCI, the OpenCitations Index of Crossref DOI-to-DOI Citations, which immediately became our principal source of open citations, the original OpenCitations Corpus being retained as a ‘sandbox’ in which to experiment with new data representations, for example those required for the Open Biomedical Citations in Context Corpus. Access to COCI was facilitated by Silvio’s development of a REST API, using his software tool RAMOSE (Restful API Manager Over SPARQL Endpoints), which enables the easily configurable deployment of a REST API over any SPARQL endpoint to an RDF triplestore [9]. We were able to organize our all data, both ‘traditional’ and new, and to encode it in RDF, thanks to the comprehensive OpenCitations Data Model [5], itself based on our SPAR Ontologies [3], which we evolved as necessary to accommodate new data representation requirements.
During this period we published a number of definitions, conference papers and journal articles documenting these advances, details of which can be found here. Of these, the most recent canonical publication describing OpenCitations as an infrastructure for open scholarship, and its datasets, tools, services and activities, is Peroni and Shotton (2020) [10]. We also established the Research Centre for Open Scholarly Metadata at the University of Bologna, primarily to handle administrative, financial and academic aspects of OpenCitations activities.
OpenCitations’ future
The problem remained: how to sustain the OpenCitations infrastructure financially. We were greatly helped by Bilder, Lin and Neylon’s formulation of the Principles of Open Scholarly Infrastructures (POSI) [11], in which they clearly pointing out that reliance solely on grant funding for specific projects was not the answer. OpenCitations compliance with POSI is described here. We were thus immensely grateful that SPARC Europe and other institutions had the wisdom to establish SCOSS (The Global Sustainability Coalition for Open Science Services) to facilitate the crowd-sourced financial support of useful open infrastructures by the scholarly community, including academic libraries, government agencies and other stakeholders. OpenCitations applied for SCOSS support in 2019, which led to the selection of OpenCitations for support in the SCOSS second round.
The donations we are now starting to receive from such stakeholders, and the new staff that this funding has recently allowed us to hire, signal the start of our transition from a financially vulnerable academic project to a sustainable open scholarly infrastructure of real value to the community.
The work of opening more of the global citation graph now requires two things:
that each publisher takes responsibility for ensuring that the references from all of its journal articles and books are submitted, together with all other bibliographic metadata, to open scholarly bibliographic metadata aggregators such as Crossref and DataCite, from which they can be indexed into open citation indexes of sufficient quality, depth of detail and breadth of coverage that these offer genuine alternatives to the expensive proprietary citation indexing services upon which the academic community presently relies; and
that the entire scholarly stakeholder community re-directs a fraction of the enormous sums currently spent on its subscriptions to proprietary bibliographic services in order to support Open Science infrastructures such as OpenCitations that making citations and other forms of scholarly metadata and objects freely available.
[3] Silvio Peroni, David Shotton (2018). The SPAR Ontologies. In Proceedings of the 17th International Semantic Web Conference (ISWC 2018): 119-136. https://doi.org/10.1007/978-3-030-00668-6_8
[4] Peroni S, Lapeyre DA and Shotton D (2012) From Markup to Linked Data: Mapping NISO JATS v1.0 to RDF using the SPAR (Semantic Publishing and Referencing) Ontologies. Proc. 2012 JATS Conference, National Library of Medicine, Bethesda, Maryland, USA (October 2012): 16-17. http://www.ncbi.nlm.nih.gov/books/NBK100491/
[6] Silvio Peroni, David Shotton, Fabio Vitali (2017). One Year of the OpenCitations Corpus: Releasing RDF-based scholarly citation data into the Public Domain. In The Semantic Web – ISWC 2017 (Lecture Notes in Computer Science Vol. 10588, pp. 184–192). Springer, Cham. https://doi.org/10.1007/978-3-319-68204-4_19
[9] Daquino, M., Heibi, I., Peroni, S., & Shotton, D. (2021). Creating Restful APIs over SPARQL endpoints with RAMOSE. Semantic Web. http://arxiv.org/abs/2007.16079
[10] Silvio Peroni, David Shotton (2020). OpenCitations, an infrastructure organization for open scholarship. Quantitative Science Studies, 1(1): 428-444. https://doi.org/10.1162/qss_a_00023
“The competitive benefits of closing access to citation data diminish with each new citation released to the public domain, but the benefits of open data remain. Going forward, citation data is almost completely public domain”.
With these words, from the article “A tipping point for open citationsdata” (July 15, 2021), Ian Hutchins celebrated the threshold crossing of one billion citations on public-domain databases in February 2021.
Now, a new significant milestone has been reached. We are enthusiastic to announce that COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations has just been extended with 334 million additional citations. Its most recent release, the COCI July 2021 release, now contains a total of 1.09 billion DOI-to-DOI citation links derived from open references within Crossref,which includes the references of articles deposited or opened in Crossref between November 2020 and January 2021.
These numbers make us proud, and confirm the essential value of the Initiative for Open Citations (I4OC). Since 2018, the mission of I4OC has been to persuade publishers to provide open citation data by means of the Crossref platform. The I4OC untiring commitment has led the major academic publishers to a progressive change of heart regarding open citations, and the scholarly community to a deeper interest in this openness.
These factors contributed to the creation of COCI in 2018, the first open citation index created by OpenCitations, in which we applied the concept of citations as first-class data entities (Heibi I., Peroni S., Shotton D., 2019). Over the last three years, COCI has been extended in a series of releases, by harvesting citations mostly from Crossref data dumps, starting from an initial coverage of 300 million citations (First release).
A crucial event that preceded (and delayed!) this latest COCI release was Elsevier’s endorsement in the DORA Declaration on Research Assessment in December 2020, thereby making “reference lists for all articles published in Elsevier journals openly available via Crossref so they can be available for reuse. This means other important initiatives like I4OC can draw on this metadata”. As described in our previous post, Elsevier’s welcome commitment led to the opening of many previously closed references from its numerous academic journals submitted to Crossref. Now, after an extended period of data ingestion and processing, all these newly opened Elsevier references are available at OpenCitations within COCI.
Elsevier’s involvement has both an effective and a symbolical value. Even if publishing more than one billion citations is a thrilling achievement, and – as Hutchins wrote – we are now at a tipping point with regard to open citations data, this milestone is not the last stop. Together with the other organizations and projects that participate in the Initiative for Open Citations, we will keep claiming the urgency for the remaining academic publishers to join our cause, and sharing our values with the whole academic community to make all existing citations data freely open and accessible. Recalling what Dario Taraborelli wrote in the conclusion of his article “The citation graph is one of humankind’s most important intellectual achievements“, “the world is waiting for the citation graph to become a public good”.
The interconnection between Wikipedia and Wikidata is now larger than ever.
The Wikipedia Citations dataset currently includes around 30M citations from Wikipedia pages to a variety of sources – of which 4M are to scientific publication. The increase of the connection with external data services and the provision of structured data to one of the key elements of Wikipedia articles has two significant benefits: first of all, a better discoverability of relevant encyclopedic articles related to scholarly studies; furthermore, the enacting of Wikipedia as a social authority and policy hub which would enable policymakers to assess the importance of an article, person, research group and institution by looking at how many Wikipedia articles cite them.
These are the motivations behind the “Wikipedia Citations in Wikidata” project, supported by a grant from the WikiCite Initiative. From January 2021 until the end of April, the team of Silvio Peroni (director of OpenCitations), Giovanni Colavizza, Marilena Daquino, Gabriele Pisciotta and Simone Persiani from the University of Bologna (Department of Classical Philology and Italian Studies) has been working in developing a codebase to enrich Wikidata with citations to scholarly publications that are currently referenced in English Wikipedia. This codebase consists of four software modules in Python and integrates new components (a classifier to distinguish citations by cited source and a look-up module to equip citations with identifiers from Crossref or other APIs). In so doing, Wikipedia Citations extends upon prior work which only focused on citations already equipped with identifiers.
In the first two steps of the workflow (extractor and converter) the mapping between the various ways Wikipedia citations are represented in Wikipedia articles and the OpenCitations Data Model (OCDM) has been implemented and then enriched with a component responsible to find new identifiers to the entities in a dataset compliant with OCDM (enricher), while in the pusher step the mapping between the OCDM and Wikidata has been enabled, and the code has been finally released in GitHub.
WCW Workflow Diagram
The extensive documentation that has accompanied the release of the codebase is crucial for one of the principal aims of the project, I.e., the adoption and reuse of the codebase by the community in other relevant Wikimedia projects, while the engagement of various communities (Wikidata, libraries, scholars…) is favored on one side by offering an increased number of citations data included in Wikidata, on the other side by blogging and sharing the updates on Twitter and public mailing lists
This project, whose ambitious purpose is to make Wikipedia contents better discoverable and enrich Wikidata with a ready-to-use corpus for further analysis or for developing new services, is opened to future perspectives. The intention is to use the software to create a dataset of Wikipedia English citations to understand, in particular, how many new entities (i.e., citing Wikipedia pages, cited articles and venues, authors) should be added to Wikidata in order to upload all the set of extracted citations, with the result of adding a massive amount of new bibliographic-related entities to the dataset.
The first steps have been taken, now we aim to extend the engagement of the community involved, especially those scholars that leverage Wikidata in existing services, and to interact with the scholars, libraries and institutions interested in a new approach to research, focused on people (from individuals to research groups) and their intellectual relevance.
We congratulate and thank Elsevier, the world’s largest academic publisher, for endorsing the DORA Declaration on Research Assessment (https://sfdora.org/), thereby joining the hundreds of other publishers and scientific organizations which have endorsed DORA over the previous eight years, and also for making a commitment to open the references from all its journal articles submitted to Crossref. The text of Elsevier’s endorsement, dated 16th December 2020, is to be found at https://www.elsevier.com/connect/advancing-responsible-research-assessment, and includes the statement:
“We will make reference lists for all articles published in Elsevier journals openly available via Crossref so they can be available for reuse. This means other important initiatives like I4OC can draw on this metadata.”
Particular thanks are due to Kumsal Bayazit, Elsevier’s CEO, and to Andrew Plume, head of Elsevier’s International Center for the Study of Research (ICSR), for spearheading this change in stance on the part of Elsevier, which until this week has been alone among the major scholarly publishers in keeping its reference lists at Crossref closed, for which it has attracted much criticism from the academic community.
This change of heart on the part of Elsevier now means that by next spring, after Crossref has had a chance to implement this change in status over the large corpus of Elsevier journal metadata, the reference lists of articles in the vast majority of the world’s academic journals will be open, enabling such metadata to be used to enhance publication discovery and enable transparent research assessment. The I4OC web site and COCI, OpenCitations Index of Crossref open DOI-to-DOI citations, will reflect this change once it has happened.
The Institute of Electrical and Electronics Engineers (IEEE), the American Chemical Society (ACS), and the University of Chicago Press now stand alone as the only significant scholarly publishers who choose not to make their publication reference lists open.
Today, we have published the bi-monthly release of COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations. In this latest release (dated 6 September 2020), we extended COCI with more than 11 million additional citations. Now, COCI contains more than 733 million DOI-to-DOI citation links between more than 59.4 million bibliographic entities.
These new citations were harvested from the most recent Crossref data dump, downloaded on 19 August 2020, which includes the references of articles deposited in Crossref between 4 June 2020 and 3 August 2020.
Ivan Heibi, Silvio Peroni & David Shotton (2019). Software review: COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations. Scientometrics, 121 (2): 1213-1228. DOI: https://doi.org/10.1007/s11192-019-03217-6
and that all the bibliographic and citation data in COCI:
are also available as dumps on Figshare in CSV, N-Triples, and Scholix; and
can be freely re-used for any purpose.
A final remark: COCI and other OpenCitations services will be the topic of a presentation that we will have in the context of the Workshop on Open Citations and Open Scholarly Metadata 2020. The workshop is a 3-hour event for researchers, scholarly publishers, funders, policymakers, and opening citations advocates, interested in the creation, reuse, and improvement, of open citation data and open scholarly metadata, with invited speakers. No registration is needed to follow it – we hope to see you there on 9 September at 15:00 CET!
Several important recent events have involved OpenCitations directly as a participant. Here we introduce some of the most significant ones:
Our interviews during a Fireside Chat with John Chodacki during the Open Publishing Fest;
The SCOSS poster about OpenCitations and the other two selected infrastructures during LIBER 2020, which won the LIBER 2020 Peoples Choice Poster Award;
The availability of two new short-term research positions with OpenCitations for our Wellcome Trust funded project (application closing deadline: 23 July 2020); and
A new release of COCI, bringing the total number of open citations available in this dataset to more than 721 million.
Open Publishing Fest
The Open Publishing Fest was a decentralized on-line public event held from 18 May to 29 May
to bring together communities supporting open source software, open content, and open publishing models.
(from the Open Publishing Fest website, last visited 4 July 2020)
Within this event, John Chodaki and Cameron Neylon organised a series of sessions named “Fireside Chats” in which they invited people from the open publishing community to discuss their careers and projects. David Shotton and Silvio Peroni were the guests in one of these chats with John Chodaki, in which we talked about the origins of OpenCitations and the plans for OpenCitations’ future. The video of our chat (see link below) is available on YouTube.
The recording of the fireside chat that David Shotton and Silvio Peroni had on May 28th 2020 with John Chodaki in the context of the Open Publishing Fest.
SCOSS at LIBER 2020: promoting open infrastructures
SCOSS, the Global Sustainability Coalition for Open Science Services, which selected OpenCitations last December as worthy of community crowd-funding support as part of its second funding cycle, participated in LIBER 2020with a poster which showcases the infrastructures that they recommend that the community financially supports.
Tweet by SCOSS on the poster presented at Liber 2020.
This poster won the People’s Choice Award and confirms the crucial activity that SCOSS is doing in making the academic community aware of the importance of providing financial support to open infrastructures like OpenCitations for the benefit of the whole of society.
SCOSS has published an article about why supporting services like those we believe in is so important not just for academia – but for society. Read it here: https://t.co/YuHO0lvFQypic.twitter.com/hMeMdHtaKV
A tweet by SCOSS on the document they wrote on the importance of supporting open infrastructures.
Furthermore, Giannis Tsakonas, Director in the Library & Information Center at the University of Patras (Greece), and a member of the LIBER Executive Board as head of its Innovative Scholarly Communication Steering Committee, shared a wonderful thread on Twitter about OpenCitations and the other open infrastructures (DOAB, OAPEN, and PKP) that have been selected by SCOSS in its second funding cycle.
A thread by Giannis Tsakonas about us and the other open infrastructures selected by SCOSS for their second funding cycle.
Short-term research positions open at OpenCitations in Bologna for our Wellcome Trust funded project
Wellcome Trust announced they have extended all their grants that were due to end in 2020 or 2021, including our Open Research Fund funded project entitled “Open Biomedical Citations in Context Corpus”. This project aims at providing data for each individual in-text reference pointer (aka in-text citation) and its semantic context, making it possible to distinguish references that are cited only once in the text of a paper from those that are cited multiple times, to see which references are cited together (e.g. in the same sentence), to determine in which section of the article references are cited (e.g. Introduction, Methods), and, potentially, to retrieve the function of each citation.
Some preliminary outcomes of the project have already been described in a recent blog post, and a preprint describing some of the activities of the project has also been also made available on arXiv. That paper focuses on the extensions we have made to the OpenCitations Data Model, used for the storage of data in all the OpenCitations datasets, to enable the additional metadata types resulting from the Citations in Context project to be recorded.
In the context of the funding extension to this Wellcome Trust project, the Department of Classical Philology and Italian Studies (FICLIT) at the University of Bologna has just opened two new positions for short-term (5 months) research fellowships from August to December 2020 inclusive, for which the application closing deadline is 23 July 2020. The main goals of these the short-term research fellowship are (a) to develop the software for handling the data stored in the Open Biomedical Citations in Context Corpus, and (b) to develop indexing mechanisms to analyse a large number of documents simultaneously within our local computing environment, without having to use external services.
The net salary for each research fellowship is 1,600 EUR per month, tax free. The minimal requirement to apply for one of these positions is to have a Bachelor degree, although higher qualifications in Computer Science would be beneficial. Since these are University of Bologna positions, the application forms are in Italian. However, the description of the activity plan of the research fellowships is available in both Italian and English. We would be happy to provide further information, and help in completing the application forms if necessary, so please do not hesitate to email us.
New release of COCI with an additional 18 million citations
Every two months we are able to publish additions to COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations. This latest release (dated 4 July 2020) extended COCI with more than 18 million additional citations, so that COCI now contains more than 721 million DOI-to-DOI citation links between more than 58.8 million bibliographic entities.
These new citations were harvested from the most recent Crossref data dump, downloaded on 8 June 2020, which includes the references of articles deposited in Crossref between 4 April 2020 and 4 June 2020. As before, we will use this new release of COCI to update the Coronavirus Open Citations Dataset, the third release of which will include details about relevant additional references and publications.
Ivan Heibi, Silvio Peroni & David Shotton (2019). Software review: COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations. Scientometrics, 121 (2): 1213-1228. DOI: https://doi.org/10.1007/s11192-019-03217-6
and that all the bibliographic and citation data in COCI:
We are excited to share that COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations, was on 12 May 2020 extended with more than 47 million additional citations, and has reached a total number of more than 702 million DOI-to-DOI citation links between more than 58 million bibliographic entities.
The citations added in this the fifth release of COCI came from the most recent Crossref dump downloaded on 22 April 2020, which includes the references of the articles deposited in Crossref between 4 October 2019 and 4 April 2020. Such updates to COCI will now occur regularly at bimonthly intervals.
As a consequence, COCI now contains 702,772,530 citations, and also includes publications about the COVID-19 pandemic. We will use this new release of COCI to update the Coronavirus Open Citations Dataset, the second release of which will include details about these additional references and publications.
As introduced in an earlier blog post and an open-access article recently published on Scientometrics, COCI is our first OpenCitations Index of open citations. In COCI, we have applied the concept of citations as first-class data entities, each identified using a unique persistent Open Citation Identifier (OCI). COCI indexes the contents of one of the major databases of open scholarly citation information, namely Crossref, and renders and makes available this information in machine-readable RDF and in other formats.
The fourth release of COCI contains more than 655 million DOI-to-DOI citation links between more than 55 million bibliographic entities. The additional 31 million citations added in the new release come from the reprocessing of previous dumps of Crossref data. In particular, we retrieved all the citations that involve references in citing articles that were in the Crossref ‘Limited’ set when we downloaded it in October 2018. Such citing articles currently appear in the Crossref ‘Closed’ dataset due to more recent restrictive policy decisions taken by their publishers.
Finally, we wish to remind you that all the bibliographic and citation data in COCI:
OpenCitations is an infrastructure organization for open scholarship dedicated to the publication of open bibliographic and citation data. We at OpenCitations are proud to announce the publication, in the first issue of Quantitative Science Studies, of a canonical paper in which we introduce and describe OpenCitations and outline its achievements and goals [1].
Here, I outline the contents of our paper, and provide definitive links on the topics described. Many of these topics have been the subjects of earlier blog posts.
This paper appears in the first Special Issue of QSS, dedicated to the description of the bibliometric data sources that lie at the heart of scientometric research, which aims to characterize the most important data sources currently available and to show how they differ in various dimensions, for instance in the data they provide, their level of openness, and their support for making research reproducible. The first three papers in this special issue cover the most important commercial bibliographic data sources: Web of Science (Clarivate Analytics), Scopus (Elsevier), and Dimensions (Digital Science), while the remaining three articles describe open data sources: Microsoft Academic, Crossref and OpenCitations.
In the second half of the paper, we describe OpenCitations as an organization in terms of its compliance with the principles for the sustainability of open infrastructures proposed by Bilder, Lin and Neylon (2015) [2], and report the selection of OpenCitations by the Global Sustainability Coalition for Open Science Services (SCOSS) as an open infrastructure organization worthy of crowd-funding support by the stakeholder community. We then provide usage statistics for our datasets and web site, and describe the adoption of OpenCitations data and services by the community, before concluding with a forward look at our proposed developments of OpenCitations activities.
References
[1] Silvio Peroni and David Shotton (2020). OpenCitations, an infrastructure organization for open scholarship. Quantitative Science Studies 1 (1): 428-444. https://doi.org/10.1162/qss_a_00023
