The incentives for new OpenCitations innovative solutions
Two years ago, in their canonical 2020 QSS paper on OpenCitations, Silvio Peroni and David Shotton anticipated the creation of the new database, OpenCitations Meta, able to “offer a faster and richer service” by storing bibliographic metadata “in house”. Meta would “avoid duplication of data by efficiently permitting us to keep […] a single copy of the metadata for each of the bibliographic entities involved as citing or cited entities in the different OpenCitations’ citation indexes”, would remove the requirement for potentially slow API calls to external metadata sources such as Crossref and ORCID, and would enable us to index citations involving entities lacking DOIs.
Important synergies to achieve goals
Today, thanks to the recent involvement of OpenCitations in two EC-funded projects, the OpenAIRE-Nexus Project (Horizon 2020 EU funded project, GA: 101017452) and the RISIS2 Project (Horizon 2020 EU funded project, GA: 824091), the development of OpenCitations Meta has commenced, with a planned release date later in 2022.
The OpenAIRE-Nexus project started in January 2021 to embrace and expand the operation of a portfolio of thirteen services, provided by OpenAIRE infrastructure, public institutions, organisations and universities, classified into three portfolios entitled PUBLISH, MONITOR, and DISCOVER. The OpenAIRE-Nexus portfolios focus on the demands of the three main categories of the research lifecycle. Therefore, OpenAIRE-Nexus makes sure such services are integrated to provide a uniform Open Science Scholarly Communication package for the European Open Science Cloud (EOSC). Within the OpenAIRE Nexus project there is scope for producing not only support materials (factsheet, guides, video tutorials, demos) but also training sessions where the services in the three portfolios will be showcased, anticipating the EOSC onboarding process. The role of OpenCitations in the project is to provide open bibliographic citations, and interconnect and integrate (and vice versa) functionalities with the OpenAIRE Research Graph and more OpenAIRE-Nexus services such as EpiSciences, OpenAIRE MONITOR) the core component of OpenAIRE infrastructure and services and of the EOSC Resource Catalogue.
Additionally, we are happy to announce our recent involvement in the RISIS2 Project. The Research Infrastructure for Science and Innovation Policy Studies (RISIS) is a project funded by the European Union under a Horizon2020 Research and Innovation Programme. RISIS2 involves 18 partners working together to create and maintain a research infrastructure for the field of Science, Technology, and Industry (STI) Studies, and to build an advanced research community in this field. OpenCitations’ contributions to RISIS2 will include not only the creation of OpenCitations Meta but also the development of a new citation index of open references, the OpenCitations Index of DataCite Open Citations (DOCI), which will be based on the open reference holdings of DataCite and, together with COCI, will be cross-searchable through our unified OpenCitations API.
Lessons learnt so far
A year into the OpenAIRE-Nexus project, we have found that one of the most significant benefits for OpenCitations is our involvement with this wide cooperative network of European research infrastructures, services, and communities, within which we can exchange experiences, ideas, and knowledge, and discuss any challenges and outcomes with our colleagues. More importantly, OpenCitations becomes positioned within the Open Science ecosystem, as a valuable innovative infrastructure with strong proof of integration and interoperable operations. Being part of the OpenAIRE-Nexus team has opened up more future challenges and expectations, and raised the bar for the inclusion of more functionalities of value. Thanks to the dedication of its efficient communication team, OpenAIRE is also helping us by communicating OpenCitations services to additional users and stakeholders, by inclusion within the comprehensive OpenAIRE services catalogue, by releasing an OpenCitations factsheet and by permitting us to present the latest information on OpenCitations through established events (i.e. Open Science FAIR 2022). FAIR and openness of information is our motto, and we strongly promote this through all our activities.
Expanding our team
As announced in our previous blog post “Five reasons why 2021 has been a great year for OpenCitations”, the support we receive from the EU as part of OpenAIRE-Nexus has enabled our recent appointment of Arcangelo Massari, a software developer who is now playing a crucial role in the creation and development of OpenCitations Meta.
As the year 2022 progresses, we look forward to bringing you further information about other new goals for OpenCitations, made possible by the support we receive from our numerous partnerships.
“What role does ‘open’ play in making this project special?”
This apparently easy, but not banal, question was asked in the Open Publishing Awards nomination form, and at OpenCitations we prefaced our answer to it by stating “For OpenCitations, ‘open’ is the crucial value and the final purpose.” We consider the free availability of bibliographic citation data to be a necessary condition for the establishment of an open knowledge graph, and believe that having citations open helps achieve a more transparent, accessible and comprehensive research practice.
Since 2019, the Open Publishing Awards, founded and organized by the Coko Foundation and sponsored by OASPA, Crossref and Cloud68.Co, “celebrate software and content in publishing that use open licenses but also, importantly, provide a chance to reflect on the strategic value of openness”. The award judges considered open access projects divided into five categories: Open Publishing Lifetime Contribution, Open Content, Open Publishing Models, Open Source Software and Open Data.
It is in this final Open Data category of the Open Publishing Awardsthat OpenCitations was selected, as an infrastructure that perfectly represents the open principles, from among the few semantic web and linked open data initiatives currently available in the scholarly communication landscape. The award was announced in the Open Publishing Awards Ceremony, during the closing session of the FORCE2021 conference “Joining Forces to Advance the Future of Research Communication” (7-9 December). You can learn more about the Awards and the other projects selected here: https://openpublishingawards.org/results/2021/index.html
The greatest honour for OpenCitations was receiving the following comment given on behalf of the jury panel, which included open source and scholarly communication experts:
“At the time of writing this review, the largest database provided by OpenCitations contains more than 1.23 billion citations. Compiling this database in a license-friendly way is a feat on its own, but combine that with OpenCitations’ persistence (established 11 years ago), their active and consistent involvement with the community, and the number of works that were made possible by their effort (Google Scholar lists 1440 results), it is clear that OpenCitations is one of the fundamental projects in open publishing, specifically in open scientific publishing”.
We are proud and humbled to count the Open Publishing Award in Open Data among the acknowledgements so far received by OpenCitations. Despite the term “award”, the Open Publishing Awards, in fact, don’t aim to proclaim winners, but rather to “shake the hands” of some projects which seem to be following (and tracing) a right path towards a more open knowledge. All the projects awarded help by defining more concretely what “open”means, and at the same time their example encourages awareness on the variety of the open publishing projects, and a reflection about the common values and goals that gather so many different people, institutions and organizations.
Recognizing the commitment to the openness of knowledge and research of the not-for-profit and collaborative projects like OpenCitations is about community, not competition.
As Silvio recently stated:
“OpenCitations is a plural. Together, we are OpenCitations.”
On September 27, OpenCitations’ director Silvio Peroni, together with Niels Stern (DOAB/OAPEN) and James MacGregor (PKP), held the online workshop “How Open Infrastructure Benefits Libraries” during the Open Access Tage 2021. Open-Access-Tage (Open Access Days) are the annual central platform for the steadily growing Open Access and Open Science community from Germany, Austria and Switzerland, and are aimed at all those involved with the possibilities, conditions and perspectives of scientific publishing.
The workshop gathered three of the SCOSS-supported infrastructures to discuss how Open Infrastructures (OIs) could encourage the engagement of university libraries, and how they could be beneficial game-changing alternative to commercial infrastructures. This theme, which was also been presented during the last LIBER conference, was here discussed under a new perspective, by involving the specific case of the libraries from the German-speaking region. Their point of view particularly emerged during the second part of the workshop, during which the participants were divided into two breakout rooms to discuss two questions each. These are the answers and comments that emerged from the discussions.
1. What would prevent or encourage libraries in the German-speaking region to support open infrastructures?
The three main concepts held to be crucial in this field were transparency, promotion and governance.
Transparency: German libraries and public institutions often deal with strict funding limitations relating to donations. It is therefore crucial for OIs (a) to present in a clear way how libraries can get involved and the money needed, (b) to communicate what they do and how they can add value to libraries compared to other services, and (c) to clarify the direct return and benefits on investments. These points would make it easier to recommend OIs internally, especially when people from subject-specific institutions are interested in subject-independent OIs. Point (b) leads to the Promotion issue: Open Infrastructures should promote themselves non only on a global level, by communicating their impact in the open research movement as against non-transparent propitiatory services, but also at a local level, by providing information about the usage (and the value) of their services at an institutional and/or national level. This case-by-case narration (with attention to the specific benefits) would make it easier for the institutions to evaluate the sustainability of the investment. An incentive to donate is being actively involved in the community governance, i.e.through a board membership.
Nevertheless, is also necessary for libraries to “take courage” when investing in such OIs, and, when possible, to overcome administrative boundaries by forming consortia. Finally, of particular note was a desire to see locally-managed sub-communities that could speak specifically to the German (or whichever) language environment, much as ORCID arranges itself.
2. Community Governance. What kind of involvement do you want to see, how do you want to be involved?
Some common problems which prevent the institutions from being involved are (a) a general concern about the fact that negotiations with publishers are typically the main focus of OA discussions – leaving little time to focus on OIs and other open initiatives, and (b) a lack of time, or of guidelines, for evaluating the different infrastructures to invest in. This is why SCOSS was appreciated as an intermediary in the decision process, because of its own rigorous evaluation and selection mechanism. The community-funding approach proposed by SCOSS thus seems to be the preferred way by which to support OIs.
Regarding community governance, one idea could be to involve interested scholars in the governance of the open infrastructures (with the library acting as an interface between the open infrastructure and the scholars) rather than only involving library staff – although this idea was argued against in the second group, as researchers are often percieved as too busy to be functional in operational infrastructure groups. What also emerged from this second question is an interest in community involvement on different levels, for example as a community of practices or through discussion boards, mailing lists, periodic meet-ups, workshops, newsletters, etc. The community could also be articulated into local sub-communities, as in the successful case of ORCID and ORCID_DE.
Authors: Ludo Waltman, Bianca Kramer, David Shotton
In this blog post, Ludo Waltman, Bianca Kramer, and David Shotton, co-founders with colleagues of the Initiative for Open Abstracts, celebrate the first anniversary of the initiative.
On September 24 last year, the Initiative for Open Abstracts (I4OA) was launched. We started the initiative as a group of colleagues working in the publishing industry, for scholarly infrastructure organizations, at university libraries, and at science studies research centers. I4OA called on scholarly publishers to make the abstracts of their published works openly available in a suitable infrastructure, preferably by submitting them to Crossref, and it continues to make this call. Openness of abstracts makes scholarly outputs easier to discover, it enables new types of research analytics, and it supports science studies research.
In this blog post, we celebrate the first anniversary of I4OA by summarizing the progress made so far and by discussing how I4OA fits into the broader landscape of many ongoing developments toward increased openness of the metadata of scholarly outputs.
How much support for open abstracts do we have?
When I4OA was launched one year ago, the initiative was supported by 40 publishers, including Hindawi, Royal Society, and SAGE, who are founding members of the initiative. Among the initial supporters of I4OA there were commercial publishers (e.g., F1000, Frontiers, Hindawi, MDPI, PeerJ, and SAGE), non-profit publishers (e.g., eLife and PLOS), society publishers (e.g., AAAS and Royal Society), and university presses (e.g., Cambridge University Press and MIT Press). Some of the initial supporters of I4OA are open access publishers, while others publish subscription-based journals.
Over the past year, the number of publishers supporting I4OA has more than doubled. The initiative is currently supported by 86 publishers. Publishers that have joined I4OA over the past year include ACM, American Society for Microbiology, Emerald, Oxford University Press, and Thieme. I4OA has also been joined by a substantial number of national and regional publishers, for instance from countries in Latin America, Eastern Europe, and Asia.
In addition to this, I4OA is supported by a large number of stakeholders in the research system, including many scholarly infrastructure providers.
— Initiative for Open Abstracts (@open_abstracts) October 19, 2020
However, Elsevier, Springer Nature, Wiley, and Taylor & Francis, the four largest publishers in terms of the number of published works, have not yet joined I4OA. These publishers appear to monetize their abstracts by selling them to abstracting services, and they seem to fear that joining I4OA may cause them to lose these revenue streams. Elsevier might also perceive openness of abstracts as a competitive threat to its Scopus business. Elsevier, Wiley, and Taylor & Francis have not yet submitted any abstracts to Crossref, while Springer Nature has started to submit abstracts, but only for its open access content.
How many open abstracts do we have?
On September 1st 2021, 12.3% of the 89.4 million journal articles indexed by Crossref had an open abstract. Focusing on the so-called current content in Crossref (i.e., content from the last three years), the share of journal articles with an open abstract is substantially higher. Of the 12.1 million journal articles in the period 2019-2021, 30.1% had an open abstract.
Figure 1 shows the increase over the past few years in the percentage of journal articles in Crossref that have an open abstract. For current content, this percentage increased from 14.9% in September 2019 to 30.1% in September 2021, clearly showing the effect of I4OA. For backfiles (i.e., content that is at least three years old), the increase is more modest, from 4.8% in September 2019 to 9.5% in September 2021. This increase reflects the efforts made by several publishers (including Hindawi, Royal Society, and SAGE, three founding members of I4OA) to make abstracts openly available not only for their new content but also for all their older content.
Figure 1. Increase in the percentage of journal articles in Crossref that have an open abstract.
The above statistics are specifically about journal articles. Looking at all content types in Crossref, including proceedings articles, book chapters, and books, the share of open abstracts is somewhat lower. On September 1 this year, 24.8% of the current content and 7.3% of the backfiles had an open abstract.
Figure 2 provides a breakdown by publisher of the percentage of journal articles published in the period 2019-2021 and documented in Crossref that have an open abstract (horizontal axis). The figure also shows the total number of journal articles of a publisher in the period 2019-2021 (vertical axis; logarithmic scale).
Figure 2. Number of journal articles of a publisher in Crossref in the period 2019-2021 vs. percentage of journal articles that have an open abstract
Publishers that support I4OA, colored orange in Figure 2, tend to have a high percentage of journal articles with an open abstract. They typically do not reach 100%, because some of the content they publish does not have an abstract. There are a few publishers that only recently started to open their abstracts, and so for these publishers the percentage of open abstracts is still relatively low. Publishers that have not yet expressed support for I4OA are colored blue in Figure 2. Most of them have a low percentage of open abstracts, and many do not have any open abstracts at all.
The progress made by individual publishers in opening their abstracts can be clearly seen by comparing Figure 2 with a similar figure published in this blog post last year.
What else happened over the past year?
A very positive development in the past year is the accomplishment of the Initiative for Open Citations (I4OC), a sister initiative of I4OA that campaigns for publishers to make the references of their published works openly available in Crossref. In the first half of 2021, Elsevier, American Chemical Society, and Wolters Kluwer all opened their references. With the exception of IEEE, all major publishers now support I4OC. This development seems to show that most publishers recognize the importance of making the metadata of their published works openly available, suggesting that many of them may also want to join I4OA.
A less positive development was the announcement made last May that Microsoft Academic will be discontinued at the end of the year. At the moment, Microsoft Academic is the most important data source for open abstracts. As shown in a recent presentation by two of the I4OA founders, more than half of the scholarly outputs indexed both by Microsoft Academic and by Crossref have an open abstract in Microsoft Academic. Only 10% of these outputs have an open abstract in Crossref. Hence, the discontinuation of Microsoft Academic will greatly reduce the availability of open abstracts, unless publishers take up their responsibility to submit abstracts to Crossref. OurResearch, which is building a replacement for Microsoft Academic, has already announced that it will only be able to make abstracts available if publishers submit them to Crossref (or PubMed).
Another important development is the growing adoption of the Principles of Open Scholarly Infrastructure (POSI). These principles aim to ensure that scholarly infrastructures serve the interests of the scholarly community, and they reduce the risk of the scholarly community losing its key infrastructures (as is happening right now with Microsoft Academic). The POSI principles have been adopted by Crossref and OpenCitations, two founding members of I4OA. OurResearch, mentioned above, has also expressed a commitment to these principles. By adopting the POSI principles, these infrastructure organizations have made a clear commitment to serve the interests of the scholarly community and to ensure the long-term availability of scholarly metadata.
Next steps
In light of the closure of Microsoft Academic at the end of the year, it is more important than ever to get broad support for I4OA. This is further reinforced by the increasing dependence of research analytics on abstracts. While research analytics based on citations continue to play an important role in research assessments and research on research (e.g., topic mapping, analyzing emerging trends and research fronts), the need to broaden the analytical toolbox is widely recognized. Many providers of research analytics are introducing new indicators and tools. In particular, analytics for assessing the contribution of research to the UN sustainable development goals (SDGs) are attracting a lot of attention (e.g., in the Times Higher Education Impact Rankings). These analytics typically identify SDG-related research by searching for specific terms (‘climate change’, ‘hunger’, ‘poverty’, and so on) in the titles and abstracts of scholarly outputs. Openness of abstracts is essential to develop a proper understanding of what these analytics do and do not tell us, and to make sure these analytics are used in a responsible way.
Publishers carry the primary responsibility for making abstracts openly available. We therefore call on publishers that do not yet support I4OA to join the initiative and to open their abstracts. The I4OA team is available to answer questions about the initiative and to provide help to publishers that want to join. Do not hesitate to contact us.
We also encourage other stakeholders in the research system to actively support openness of abstracts. As shown in Figure 3, in a recent Metadata 20/20 webinar, participants mentioned abstracts as the most important metadata element for which openness should be an essential requirement in negotiations with publishers. This highlights the crucial contribution that research institutions and research funders can make by mandating openness of abstracts in their agreements with publishers.
Figure 3. Metadata elements to be negotiated with publishers, as discussed by participants in a recent Metadata 20/20 webinar.
This blog post is published under a CC BY 4.0 license.
With the numerous September events in which the OpenCitations’ directors have recently been involved behind us, it is now time to announce the participation of our director Silvio Peroni in two October events.
On Wednesday 6th, Silvio will take part in the Beilstein OpenScience Symposium 2021 (October 5-7), giving a short presentation “Open Citations, an Open Infrastructure to Provide Access to Global Scholarly Bibliographic and Citation Data” during the Poster Flash Talk Presentation (17:10-18:00 CEST). The Beilstein OpenScience Symposium is an annual event that gathers leaders in the FAIR and Open Data movement, covering a wide range of research fields, including biomedical research, physics and social science, and exploring how open data practices are transforming sectors outside academia. The 2021 online edition will present a series of talks addressing the many ways that data transparency contributes to the research progress. Among them, the poster presentations involve short oral presentations on Wednesday, 6th October, to accompany the posters that will be displayed throughout the entire symposium. Poster abstracts are available in the Abstract Book that can be downloaded on Beilstein Symposium’s website: https://www.beilstein-institut.de/en/symposia/open-science/program/ .
The poster and slides from the presentation are available on Zenodo:
Peroni, S. (2021, October 6). Open Citations, an Open Infrastructure to Provide Access to Global Scholarly Bibliographic and Citation Data—Poster Flash Talk Session slides. Beilstein Open Science Symposium 2021, Virtual Event. Zenodo. https://doi.org/10.5281/zenodo.5553025
Peroni, S., Shotton, D. W., & Di Giambattista, C. (2021). Open Citations, an Open Infrastructure to Provide Access to Global Scholarly Bibliographic and Citation Data. https://doi.org/10.5281/zenodo.5553040
The second event is the annual European Computer Science Summit (ECSS), organized by Informatics Europe and involving academics, industry leaders, decision makers and others interested in Informatics/Computer Science research and education in Europe. ECSS 2021, “Informatics for a Sustainable Future” (Oct. 25-27), will be held as a hybrid event, involving both online as well as on-site sessions held in Madrid, at the Facultad de Ciencias de la Actividad Física y del Deporte (INEF), Universidad Politécnica de Madrid located at Calle de Martín Fierro, 7.
During the last day of the meeting (Oct. 27), Silvio Peroni will be speaking at the “National Informatics Associations Workshop”, an annual workshop organised by Informatics Europe in collaboration with the National Informatics Associations in Europe. This year the workshop will address the themes Informatics in Interdisciplinary Curricula and Research Evaluation in Informatics, thus focusing on an important question: how to recognise, assess and credit research contributions specific to Informatics, such as conference publications and software artefacts. Elaborating on this, Silvio’s talk (to be delivered in person, rather than online!) is entitled “Open citations in Informatics” (9:00 CEST).
We thank Beilstein Institute and Informatics Europe for involving OpenCitations in these international events, which provide opportunities to promote the OpenCitations infrastructure and services in stimulating environments.
Open Science Fair is an initiative of OpenAIRE, co-organized by the following key international initiatives in the area of Open Science: COAR, EIFL, Force11, LA Referencia, LIBER, OPERAS, Sparc and Sparc Europe. A biannual event, it brings together “perspectives from different actors” and “suggests ways in which communities can work together to produce roadmaps for the implementation of Open Science”. The 2021 online event saw the participation of distinguished speakers in keynote talks, roundtable discussions, workshops and training sessions. At OpenCitations, we are grateful and proud to have been invited to participate in this collaborative and inspiring virtual fair.
The Lightning Talk “ScholeXplorer and OpenCitations as the new frontier of open citation indexing” was a presentation by Silvio Peroni, co-authored with Paolo Manghi (OpenAire), Alessia Bardi (CNR-ISTI), and Sandro La Bruzzo (CNR-ISTI), describing two of the 14 open data services included in the MONITOR portfolio of the OpenAIRE-Nexus project that are used to monitor Open Science, research impact and open citations – the domains of interest of the two services presented. ScholeXplorer provides access under a CC-BY license to a huge set of links between datasets and scholarly publications, while OpenCitations, as an open infrastructure for open bibliographic metadata and citations, grants access to more than 1.18 billion DOI-to-DOI citation links, released with a CC0 public domain waiver. Both services also provide tools that allow users to query their data, with the common final goal of providing open links between scholarly resources and making them available within the OpenAire Research Graph.
As Silvio Peroni recalled, last July this article by Ian Hutchins:
B. Ian Hutchins; A tipping point for open citation data. Quantitative Science Studies 2021; 2 (2): 433–437. doi: https://doi.org/10.1162/qss_c_00138
This workshop involved Agata Morka and Vanessa Proudman from SCOSS, and representatives of the three Open Science Infrastructures involved in the Second SCOSS Funding Cycle, namely Silvio Peroni (OpenCitations), Niels Stern (DOAB/OAPEN), and James MacGregor (PKP). The starting topic of the Workshop, in which the funder perspective was provided Jean-Francois Lutz (University of Lorraine), was the paradox: although the scholarly community increasingly relies on Open Science Infrastructures, it seems very difficult to get them “to realize that there are some operational and development costs related to their existence”. In this discouraging environment, SCOSS plays a crucial role in promoting such services to potential supporters. The most recent SCOSS annual survey, presented by Jon Treadway (Great North Wood Consulting) during the workshop and involving 217 institutions from across the world, helps us understand the impact and external perception of SCOSS on a global scale. It revealed a correspondence between the geographical areas in which SCOSS is best known and the locations of the major supporters, which perhaps should not surprise us. More importantly, it found that, in addition to interoperability and global significance, community governance was one of the most important aspects of the infrastructures that institutions chose to invest in. In particular, the chance to be directly involved in governance was found to act as a great incentive for university libraries to invest in external infrastructures. Community governance is a core aspect of the Principles for Open Scholarly Infrastructures and, as underlined in this blog post, OpenCitations is working hard to achieve full compliance.
Obstacles to offering support were found to include administrative barriers, although these could be reduced if individual supporters joined consortia. Overall, however, such administration hurdles were minor issues. More significantly, some institutions were unable to pledge funds in the short term, and there was seen to be a need to raise awareness of the necessity of generating cultural change around the issue of community support. As Vanessa Proudman underlined, it is crucial to create dialogue with institutions and libraries, in order to foster the understanding that supporting Open Science Infrastructures could be beneficial for both students and researchers, and a realization that the minimum annual contribution requested by SCOSSfrom any one libraryto support such an infrastructure was less than a single article processing charge (APC), trivial in comparison with the huge annual institutional subscriptions for access to journals and citation indexes.
In a separate SCOSS interview, Marin Dacos (Open Science Advisor to the Director-General for Research and Innovation at the French Ministry of Higher Education, Research and Innovation) defined Open Science Infrastructures as “a common good of the scholarly community”, distinctly different from the services of commercial publishers. An essential value of an Open Scholarly Infrastructure is its community engagement and, from this perspective, the community funding approach promoted by SCOSS is the most efficient. As Silvio Peroni said, “What after SCOSS? SCOSS helps in creating a community around the service, and this community remains even after the three-year period of SCOSS promotion is over”.
Maybe, by fostering this growing global network of institutions and services committed to promoting a more open research, Open Scholarly Infrastrucutres can find an answer to the question “How can we not be invisible?” and achieve not just ‘sustainable’ but sustained funding from the academic community.
No-one is quite sure of the total number of scholarly publications within the global corpus. Indeed that number will be strongly influenced by the degree to which, in addition to books and journal articles, one includes within the definition of scholarly publications ‘grey literature’ such as reports published by official bodies, patents, etc. Consequentially, the total number of scholarly references within those publications is also unknown, and this number too will vary according to the inclusion criteria chosen. Furthermore, Crossref Event Data and similar datasets recording social media mentions of journal articles in blog posts and tweets extends the concept of a reference beyond that used in ‘conventional’ citation indexes such as COCI.
We celebrate the fact that well over one billion bibliographic citations are now openly available under CC0 waivers in NIH OCC (the National Institutes of Health Open Citation Collection) [1,2] and COCI (the OpenCitations Index of Crossref DOI-to-DOI Citations) [3]. Despite present gaps in their coverage, they include references to all the most important publications within the global corpus, because these will all have been cited multiple times.
Open references available from Crossref and other aggregators and indexes
Crossref, with over 1.6 billion open references, is the largest single source of such bibliographic metadata. Significant numbers of references are also available in a variety of other databases, repositories and indexes.
NIH OCC (the National Institutes of Health Open Citation Collection) is a merger of several citation databases, drawing on PubMed for crucial article metadata, and augmenting this with information from full-text articles that have been made freely available on the internet [1]. The CiteSeerX database, the arXiv preprint repository, and the Dryad data repository are examples of different types of infrastructure that also publish open bibliographic references, while there is further availability of article references from open aggregators such as DataCite and Wikidata. These may either use their own DOIs, DOIs from the Crossref DOI registration agency, or no DOIs at all. Either way, those references will not appear in Crossref.
What is lacking is semantic coherence and interoperability between these sources, permitting federated queries across them. This makes difficult the task of obtaining a comprehensive overview of the availability of open bibliographic references.
However, there are even more citations that are not yet freely and easily available anywhere in bulk, relating to the reference lists within publications of a number of distinct types. This blog post explores academia’s missing references – those that have not yet been documented within open freely accessible citation indexes – and what might be done to bring these into the public domain.
1 References that are closed at Crossref
Eight years ago, I wrote
“In this open-access age, it is a scandal that reference lists from journal articles — core elements of scholarly communication that permit the attribution of credit and integrate our independent research endeavours — are not readily and freely available for use by all scholars.” [4]
I stand by that statement, and, through OpenCitations [5], I have been working with colleagues to rectify the situation, as I described in my previous post. The Initiative for Open Citations (I4OC) can rightly be applauded for its part in encouraging almost all the major academic publishers who deposit references at Crossref to make them open.
The only major scholarly publisher not to be listed as an I4OC Participating Publisher is the Institute of Electrical and Electronics Engineers (IEEE), that, having deposited at Crossref reference lists for 58% of its preprints and publications, persists in keeping these deposited references closed and unavailable for indexing and re-use. It is to be hoped that IEEE will now realize that what it looses by not having references openly available outweighs any benefits it might have received from keeping them closed, and will join its fellow publishers in ensuring that its Crossref-deposited references are made open, both for its current issues and for its back-number journal articles. I thus call again upon IEEE to change its present position, as both Elsevier and the American Chemical Society had the courage to do recently, and to instruct Crossref to open all IEEE references. A single email to Crossref Support, with the instruction “Open all references”, is all it would take!
References in Crossref are either open, ‘limited’ or closed. Limited references are available to those subscribing to Crossref Metadata Plus, which includes OpenCitations, but not to the general public. Closed references are not freely available to anyone. The following table shows the number of Crossref works in each category, and the number of references within those categories.
Works
References
Average references per work
Total
126,627,618
Without references
70,477,843 (55.7% of total)
With references
56,149,775 (44.3% of total)
1,734,831,311
30.9
Open
49,274,155 (38.9% of total)
1,605,120,229
32.6
Limited
2,933,323 (2.3% of total)
66,459,704
22.7
Closed
3,942,297 (3.1% of total)
63,251,378
16.0
Table 1. Numbers of works and their references recorded in Crossref on 31 July 2021.
2 References not deposited at Crossref for publications with Crossref DOIs
The number of works with Crossref DOIs that lack submitted references is surprisingly large. As of 31 July 2021, 70,477,843 publications (55.7% of all works recorded at Crossref) lacked deposited references (Table 1).
Crossref classifies all types of journal content, including editorials, book reviews and letters, as “journal articles”, thus some of these works without deposited references genuinely lack them. However, the majority are conventional journal articles and books with reference lists that the publishers have simply not deposited at Crossref along with the other metadata for these works.
The average number of references per Crossref work with deposited references is 30.9 (Table 1). If, to make allowance for those works that genuinely lack references, we assume a conservative average of 25 references per work for the 70,477,843 works lacking deposited references, this means that there are over 1.75 billion references within these works that have not been deposited at Crossref, and thus are not conveniently available for indexing and reuse.
These missing references relate both large publishers that have submitted references for only some of their publications, and small publishers that perhaps lack, or think they lack, the resources to deposit any reference lists in addition to the other metadata they are already sending to Crossref for each of their DOIs. However, there are several easy methods for depositing reference lists, as detailed by Crossref here. So I encourage all publishers who are supportive of Open Science to update their procedures and commence or complete the deposition of their publication reference lists at Crossref, starting with their current issues. Crossref Support will provide assistance if required. Note that a publisher does not have to subscribe to the Crossref Cited-by service to deposit its references!
3 Citations missing in COCI: open references in Crossref to publications lacking DOIs
COCI is the OpenCitations Index of Crossref DOI-to-DOI Citations, and, as the name suggests, it indexes Crossref open references from works with Crossref DOIs to other works that have DOIs [3]. It therefore does not index open references in Crossref to works that, for whatever reason, lack DOIs.
The most recent (September 2021) release of COCI, based on the August Crossref dump, contains 1,186,958,898 citations between 69,074,291 unique work, comprising 51,103,720 citing bibliographic resources bearing Crossref DOIs and 56,105,783 cited bibliographic resources. Of the cited bibliographic resources, 38,135,212 bear a DOI issued by Crossref and have open or limited references (thus also being COCI citing resources), while 17,970,571 either have a Crossref DOI but lack open or limited references or have a DOI issued by another DOI registration agency such as DataCite (thus not being COCI citing resources).
Note that in Crossref, the ratio of works with open or limited references to works without open or limited references is 0.7:1 (Table 1). However, in COCI, the ratio of cited works with Crossref DOIs containing open or limited references to all other cited works is 2.1:1. Thus works with Crossref DOIs containing open or limited references are three times more likely to be cited than works that either have a Crossref DOI but lacking open or limited references or have a DOI issued by another DOI registration agency. This is most likely because the most important journals from almost all the larger publishers now have open references. However, it is still a remarkable ratio.
Because references to works lacking DOIs are not included in COCI, the average number of bibliographic references per citing article in COCI is only 23.2, in contrast to the numbers of references to works of all types given in Table 1.
From these data, it can be seen that there are over 480 million open Crossref references to a wide variety of works lacking DOIs that OpenCitations does not index in COCI. This is because of an intentional and fundamental limitation in the structure of the Open Citation Identifier (OCI) [6], requiring both citing and cited publications to have identifiers of the same type, that lies at the heart of the functionality of our OpenCitations Indexes.
OpenCitations is currently developing a solution that, without compromising that intentional design limitation in OCIs, will nevertheless permit us to index and publish these ‘missing’ references as Linked Open Data. We will report on this development in due course.
Crossref Event Data is a Crossref service / database that records mentions of publications bearing Crossref DOIs in social media including tweets and blog posts, and in other non-traditional citation sources such as news items and Wikipedia articles. From today (Thursday 23rd September 2021), Crossref Event Data will start to include in its holdings open references from publications bearing Crossref DOIs to other publications bearing DOIs. Limited and closed references will not be included. Initially, open references from current publications will be included in Crossref Event Data, with open references from older works with DOIs being added later. In that respect it will come to resemble COCI, except that COCI also included ‘limited’ references, treats citations as first-class data entities with their own identifiers, and makes its citation data available in RDF as Linked Open Data, as well as via a REST API. Subsequently, Crossref Event Data will also record references to publications with other forms of identifier, as OpenCitations also plans to do.
4 References available on publishers’ web sites
Many publishers, particularly those of Open Access works, already make their publication reference lists openly available on their own web sites. While this is commendable, it is not sufficient, since, if scholarly references are not made available in a centralized aggregator such as Crossref from which they can be conveniently harvested in bulk for analysis and re-use, they are much more difficult to access.
Scraping references from the HTML of individual web sites is difficult, time-consuming and liable to be incomplete. While Microsoft Academic achieved considerable success in scraping references from publishers’ web sites, possible because of the special relationships these publishers have with the Microsoft search engine Bing, this service will unfortunately soon no longer be available, illustrating a problem inherent with scholarly infrastructures provided by commercial companies that do not adopt the Principles of Open Scholarly Infrastructures.
A consequence is that such publications will become increasingly ‘invisible’, as bibliographic and analytical services come to rely more and more on centrally available data.
6 References within PDFs of scholarly works lacking DOIs
There is a large but unknown quantity of reference-containing books, academic reports, patents and journal articles from publishers that, for their own good reasons, choose not to use DOIs. The text of many of these publications is already available in a marked-up machine-readable format such as JATS, used in preparation for publication, from which the reference lists could easily be extracted. Other publications are only available as PDFs, both as published Versions of Record, or as preprints deposited in a variety of preprint repositories such as arXiv or CORE. Mining reference lists out of PDFs required expertise in text mining and AI technologies, and is labour-intensive, since it usually required the tuning of extraction algorithms to handle the particular styles and formatting of individual journals, one at a time. Two stages are involved: first, the recognition and extraction of the text of the individual references from the PDF, and second the parsing of each text string into the component parts of the reference (author names, title, publication year, etc.) A considerable number of the citations within NIH-OCC have been obtained in this manner [1], commercial companies such as Lexical Intelligence specialize in this area, and publicly available software such as GROBID is available for the purpose. However, the overall task of extracting ‘missing’ academic references from the global PDF corpus is daunting in magnitude and would require a well-funded organization.
The correct way to proceed would be for each publisher to take responsibility for liberating the references of their own publications, whether or not the publications themselves are open access, and whether or not these references are already available in a marked-up machine-readable format or only within PDF documents. Then, if the publisher still chose not to use DOIs and to submit these metadata to Crossref, these references could be submitted directly to OpenCitations for aggregation and publication as Linked Open Data.
Conclusion
From the foregoing discussion it is clear that the academic community has a long way to go before the majority of scholarly citations, the products of their own labours, are openly available for analysis and re-use. We at OpenCitations are working to address these issues and to publish more of these missing citations. However, completion of the task will require a coordinated collaborative international effort.
Are you willing to be involved?
References
[1] B. Ian Hutchins et al. (2019). The NIH Open Citation Collection: A public access, broad coverage resource. PLoS Biol.17 (10): e3000385. https://doi.org/10.1371/journal.pbio.3000385
[2] B. Ian Hutchins (2021). A tipping point for open citation data. Quantitative Science Studies2 (2): 433–437. https://doi.org/10.1162/qss_c_00138
[3] Ivan Heibi, Silvio Peroni, David Shotton (2019). Software review: COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations. Scientometrics121 (2): 1213-1228. https://doi.org/10.1007/s11192-019-03217-6
[5] 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
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;
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 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.