Open Data – OpenCitations blog

OpenCitations’ renewed compliance with the Principles of Open Scholarly Infrastructure (April 2026)

OpenCitations has formally adopted the Principles of Open Scholarly Infrastructure (POSI) since its first self-assessment in August 2021. At that time, we had only recently been included in the SCOSS funding round and, although we had a clear vision of what we wanted to build and the role we wanted to play within the Open Science ecosystem, both our financial and human resources were still very limited. For this reason, the POSI self-assessment proved to be an important exercise, since it allowed us to critically reflect on both the strengths we could build upon and the weaknesses we needed to address as we developed OpenCitations into a sustainable, community-governed Open Science infrastructure.

That first assessment highlighted some key areas of attention. In particular, it highlighted the limited executive power of the community bodies involved in governance, as well as challenges related to long-term financial sustainability, particularly the ability to generate and manage financial surpluses.

Between 2021 and 2026, OpenCitations has evolved significantly, becoming a more complex infrastructure by expanding both the services it offers and the number of data sources it integrates. During this period, we have also expanded our team, worked on the development of a container-based infrastructure, and relaunched our governance framework.

These developments made it necessary to update our POSI self-assessment. This update is also timely, given the recent release of POSI Version 2 in October 2025. The new version of the principles is the result of a collective effort by POSI adopters and includes several clarifications to existing principles (for example, around the concept of lobbying and the distinction between transparent governance and transparent operations). In addition, new principles have been introduced to better reflect how scholarly infrastructures operate within the broader research ecosystem.

We are therefore happy to share our updated POSI self-assessment, which provides a comprehensive snapshot of OpenCitations as of April 2026. At the same time, it represents a renewed declaration of our commitment to the POSI principles.

Disclaimer. As with many early POSI adopters, our previous assessment used a traffic-light system to indicate the level of alignment with each principle. In this system:

Green indicates that the principle is fully met and evidenced in practice.

Yellow indicates that the principle is partially met, with active steps underway to achieve full alignment.

Red indicates that the principle is not currently met, or that compliance is not feasible.

During the POSI Version 2 working group discussions, it emerged that the use of this traffic-light system is not mandatory for POSI self-assessments. Nevertheless, we have decided to maintain this approach, as we believe it remains particularly effective as a communication tool and, at the same time, ensures continuity with our previous assessment. We have, however, taken the liberty of adding one more element: a symbol to indicate where we were already “green” in 2021, but have further improved our performance.

The symbol is therefore a “plus” placed next to the green traffic light.

Coverage across the scholarly enterprise

OpenCitations demonstrates broad coverage by collecting citation data from global scholarship, ensuring representation across disciplines, geographic areas, and research communities. The scope of OpenCitations’ coverage is universal, not limited to a particular scholarly domain, nor to the English language, nor restricted by imposed acceptance criteria.

Stakeholder governed

Governance is structured to reflect the stakeholder community, with the International Advisory Board elected by the Council of members and responsible for approving the Trustee Network. For more information: https://opencitations.net/governance/

Non-discriminatory participation or membership

Membership is open to all individuals and organisations that support Open Science principles, enabling inclusive and non-discriminatory participation in line with OpenCitations’ founding values.

Transparent governance

OpenCitations maintains a high level of transparency by publicly documenting its organisational structure, governance processes, and decision-making procedures. Reports and relevant documentation are shared with the community, including annual reports and the Rules of Membership and Organizational Bodies.

Cannot lobby

OpenCitations does not engage in political or financial lobbying activities. Its role remains focused on supporting the scholarly community without pursuing regulatory changes that would advantage its own position.

Living will

A clear long-term stewardship strategy is in place, ensuring that data, services, and infrastructure can be responsibly transferred if needed. This is supported by a recently implemented fully replicable technical infrastructure and a new governance model designed to facilitate handover thanks to the presence of the Trustee Network, which is capable of appointing new hosting members to physically and administratively host the infrastructure.

Regular review of purpose and community value

OpenCitations has recently monitored its relevance and community value through mechanisms such as community surveys. In addition, it has established governance and technical strategies to support a responsible wind-down process, including, if necessary, the transfer of assets and infrastructure through its Trustee Network. Additionally, the Trustee Network is responsible for regularly monitoring OpenCitations’ adherence to its mission and values, as well as its annual activities and finances.

Transparent operations

OpenCitations ensures a high level of operational transparency by openly providing key documentation, including financial reports, a public roadmap, a mission statement and value proposition, a sustainability model and fee structure, and privacy policies.

Time-limited funds used only for time-limited activities

Grant income is restricted to funding specific, time-limited projects, including the appointment of personnel working on them, while core operations are not dependent on such funding.

Goal to generate surplus

Thanks to memberships and donations, as well as in-kind support from the University of Bologna, OpenCitations has recently achieved the financial capacity to ensure stability until 2029, at least, in terms of funds allocated for staff salaries and technical operational expenses.

Establish and maintain financial reserves guided by policy

Although OpenCitations has reached a level of financial stability that ensures a budget surplus, there is currently no formal financial policy defining the amount of reserves to be allocated for a transition or wind-down plan, or to address exceptional or unforeseen events. However, OpenCitations has already initiated the necessary consultations to develop a Financial Reserve Policy, which will not only define the level and management of reserves but also provide a clear framework for handling revenues. In addition, it will establish and formalise procedures for approving both budget forecasts and actual expenditures.

Mission-consistent revenue generation

Revenue generation is aligned with the organisation’s mission (in particular, the value proposition according to which “external financial support is required from the stakeholder community to support OpenCitations and enable it to expand its delivery of high-quality comprehensive open bibliographic and citation metadata”), primarily through community funding via membership fees and donations. OpenCitations‘ members are listed on the website: https://opencitations.net/members-and-donors/

Revenue generated from services, not data

OpenCitations charges no fees for any of its services, access to its data, or reuse of its software. OpenCitations members, donors and third parties all have equal free access.

Volunteer labour

OpenCitations’ core operations are carried out by paid staff, ensuring that the continuity and reliability of its services do not depend on volunteer labour. Nevertheless, OpenCitations recognises the value of voluntary labour. Indeed, the document Rules of Membership and Organizational Structure specifies that membership of the International Advisory Board is honorary and without remuneration, and that the Hosting Entity will reimburse all reasonable expenses related to travel, accommodation, and meals incurred in attending meetings, within the limits of the budget allocated for such purposes. While this is already stated in the governance framework, it is important to reiterate and further formalise it within the Financial Policy document currently under development. More broadly, the OpenCitations Mission Statement emphasises the importance of community engagement (voluntary and non-remunerated) through, for example, the involvement of community actors in the direct provision and curation of OpenCitations data, as well as the broader role of the community in supporting funding and participating in governance.

Transition planning

Transition planning is only partially developed. While the governance structure is in place, ensuring a management handover through the possibility of changing the hosting member upon approval by the Trustee Network, there is a lack of detailed operational documentation for individual roles within the management and technical teams, which may limit the organisation’s ability to ensure immediate continuity in the event of key personnel changes.

Open source

All OpenCitations software is released under open source licences, ensuring full transparency, reusability, and the possibility for the community to inspect, modify, and replicate the infrastructure.

Open data

To ensure the greatest possible reusability, all OpenCitations data is published under a Creative Commons CC0 Public Domain Waiver that permits downloading and re-use of any nature, including added-value re-purposing and commercial exploitation.

Available data

Data are provided through multiple access points, including REST APIs, SPARQL endpoints, query interfaces, and downloadable data dumps. This ensures broad accessibility and supports diverse use cases across the community.

Patent non-assertion

OpenCitations commits not to pursue patents, ensuring its infrastructure remains fully open and replicable.

Prioritise interoperability and open standards to ensure continuity and resilience

The infrastructure has been redesigned as a container-based solution, thereby facilitating replication, deployment across different environments, and long-term service continuity.

Transparency meets open citations

This post was first published on QUERTY: musings from the rabbit hole, a blog by Silvio Peroni

In the scholarly ecosystem, a bibliographic citation is a conceptual directional link from a citing entity to a cited entity, used to acknowledge or ascribe credit for the contribution made by the author(s) of the cited entity. Citations are one of the core elements of scholarly communication. They enable the integration of our independent research endeavours into a global graph of relationships that can be used, for instance, to analyse how scholarly knowledge develops over time, assess scholars’ influence, and make wise decisions about research investment.

A copyrighted fact

However, as citation data, i.e. pieces of factual information aiming at identifying entities and relationships among them, are of great value to the scholarly community, it has been a “scandal” that they have not been recognised as part of the commons. Indeed, only recently we have seen some efforts – such as the Initiative for Open Citations (I4OC) – that have tried to change the behind-the-paywall status quo enforced by the companies controlling the major citation indexes used worldwide, convincing scholarly publishers to support the unrestricted availability of scholarly citation data by publishing them in suitable open infrastructures, such as Crossref and DataCite.

Of course, as for many other kinds of data, putting bibliographic and citation data behind a paywall is a thread to enabling the full reproducibility of research studies based on them (e.g. in bibliometrics, scientometrics, and science of science domains), even when such studies are published in open access articles. For instance, the results of a recent open access article published on Digital Scholarship in the Humanities, which aimed to analyse the citation behaviour of Digital Humanities (DH) research across different proprietary and open citation databases, are not fully reproducible since the majority of the databases used – namely Scopus, Web of Science, and Dimensions – do not make their bibliographic and citation data openly available.

In addition, the coverage of publications and related citations in specific disciplines, particularly those within the Social Sciences and the Humanities (SSH), is inadequate compared to other fields. Usually, this is due to the limited availability of born-digital publications accompanied by a wide variety of publication languages, publication types (e.g. monographs), and complex referencing practices that may limit their automatic processing and citation extraction. As a side effect, such a partial coverage may result in a considerable bias when analysing SSH disciplines compared to STEM disciplines that usually have better coverage in existing citation databases.

Reforming research assessment

All these scenarios have at least another negative effect on the area strictly concerned with the research assessment, which often uses quantitative metrics based on citation data to evaluate articles, people, and institutions. Indeed, the unavailability and partial coverage of bibliographic and citation data create an artificial barrier to the transparency of the processes used to decide the careers of scholars in terms of research, funding, and promotions.

In the past years, several initiatives around the world have highlighted the importance of reforming research assessment exercises, such as those summarised in the following figure: the Frech National Plan for Open Science, the San Francisco Declaration on Research Assessment, the Leiden Manifesto for Research Metrics, and the recent proposal for a reform of the research assessment system by the European Commission. All these initiatives agree on a few essential characteristics necessary for having a trustful assessment system:

to be open and transparent by providing machine-readable, unrestricted and reusable data and methods for calculating the metrics used in research assessment exercises, and
to leave to the research community, instead of commercial players, the control and ownership of the crucial infrastructures and tools used to retrieve, use and analyse such data within research assessment systems.

Thus, the leading guideline that can be abstracted is to follow Open Science practices even when assessing research and not only when performing research.

Some initiatives pushing for reforming the principles behind research assessment systems.

Introducing OpenCitations

Within this context, OpenCitations (full disclosure: I am one of its directors) plays an important role, acting as a key infrastructure component for global Open Science, and pushes for actively involving universities, scholarly libraries and publishers, infrastructures, governments and international organisations, research funders, developers, academic policy-makers, independent scholars and ordinary citizens. The mission of OpenCitations is to harvest and openly publish accurate and comprehensive metadata describing the world’s academic publications and the scholarly citations that link them, with the greatest possible global coverage and subject scope, encompassing both traditional and non-traditional publications, and with a breadth and depth that surpasses existing sources of such metadata, while maintaining the highest standards of accuracy and accompanying all its records with rich provenance information, and providing this information, both in human-readable form and in interoperable machine-readable Linked Open Data formats, under open licenses at zero cost and without restriction for third-party analysis and re-use.

For OpenCitations, open is the crucial value and the final purpose. It is the distinctive mark and founding principle that everything OpenCitations provide – data, services and software – is open and free and will always remain so. OpenCitations fully espouses the aims and vision of the UNESCO Recommendations on Open Science, complies with the FAIR data principles, and promotes and practises the Initiative for Open Citations recommendation that citation data, in particular, should be Structured, Separable, and Open.

The most important collection of such open citation data is COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations. The last release, dated August 2022, contains more than 1.36 billion citation links between more than 75 million bibliographic entities that can be accessed programmatically using its REST API, queried via the related SPARQL endpoint, and downloaded in full as dumps in different formats (CSV, JSON, and RDF).

Collaborations between OpenCitations and other Open Science infrastructures and services.

In addition to the publication of citation data, a considerable effort has been dedicated to collaborating with other Open Science infrastructures working in the scholarly ecosystem, as summarised in the figure above. Since 2020, OpenCitations has significantly benefited from the scholarly community that resulted from the 2019 selection by the Global Sustainability Coalition for Open Science Services (SCOSS) of OpenCitations as a scholarly infrastructure worthy of financial support. The community funding permitted the appointments of people dedicated to the administration, communication, community development, and maintenance and improvement of the OpenCitations software and the computational infrastructure on which it runs. In addition, OpenCitations started its involvement with OpenAIRE and the European Open Science Cloud (EOSC), and it is collaborating with other funded projects project such as RISIS2, OutCite, OPTIMETA and B!SON.

While OpenCitations is currently providing a good set of citation data, which is already approaching parity with other commercial citation databases and that has already been used in a few studies for research purposes, there is still a margin for improvement. Currently, the citations included in the OpenCitations Indexes come mainly from Crossref data, one of the biggest open reference providers. However, Crossref does not cover all the publishers of DOI-based resources. Indeed, other DOI providers, in some cases, expose citation relations in their metadata, such as DataCite. In addition, DOI-based publications represent just a limited set of all the bibliographic entities published in the scholarly ecosystem. Other identifier schemas have been used to identify bibliographic entities – and, for some publications, there not exist identifiers at all!

Thus, to address these two issues, OpenCitations is working on expanding its coverage according to two different directions. On the one hand, OpenCitations is developing two new citation indexes of open references based on the holdings of DataCite and the National Institute of Health Open Citation Collection, which, together with COCI, will be cross-searchable through the Unifying OpenCitations REST API.

On the other hand, OpenCitations has started working to create a new database entitled OpenCitations Meta, which will provide three major benefits. First, it will permit storing in-house bibliographic metadata for the citing and cited entities involved in all OpenCitations Indexes, including author identifiers using ORCID and VIAF identifier schemes where available. Second, it will provide better query performance than the present API system, which obtains bibliographic metadata on-the-fly by live API calls to external services, such as Crossref and DataCite APIs. Finally, it will permit indexing citations involving entities lacking DOIs, by providing them OpenCitations Meta Identifiers.

This last collection, combined with automatic tools for citation extraction from digital formats, is crucial for increasing the coverage of underrepresented disciplines and fields in bibliographic databases, such as SSH publications. One of the OpenCitations’ goals is to reduce this gap in citation coverage by setting up crowdsourcing workflows for ingesting missing citation data from the scholarly community (e.g. libraries and publishers). In the future, another contribution will be to set up tools for automatic extraction of citations that can also support small and local publishers, crucial assets for SSH research, that may find difficulties in carrying out citation extraction tasks on their own since using and maintaining a tool (or paying a company addressing those tasks on behalf of the publisher) requires extra costs beyond publishers’ finances.

To conclude: OpenCitations is one piece of a puzzle that is working to change existing scholarly practices to create an open and inclusive future for science and research in which the scholarly community owns and is responsible for its own data.

Disclaimer: This text was created during the TRIPLE Booksprint “The role of open metadata in the SSH scholarly communication” and is intended to be a contribution to the “Guidelines on the research data in the humanities” deliverable (8.5) of the TRIPLE project which will be made publicly available under the CC-BY 4.0 license.

OpenCitations receives the Open Publishing Award in Open Data

“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.”

OpenCitations’ compliance with the Principles of Open Scholarly Infrastructure

What should an open scholarly infrastructure look like?

An answer to this tough question can be found in the original February 2015 blog post by Geoffrey Bilder, Jennifer Lin and Cameron Neylon

Bilder G., Lin J., Neylon C. (2015) Principles for Open Scholarly Infrastructure , http://dx.doi.org/10.6084/m9.figshare.1314859

and in the summary of the principles to be found as:

Bilder G, Lin J, Neylon C (2020), The Principles of Open Scholarly Infrastructure, https://doi.org/10.24343/C34W2H :

“Infrastructure at its best is invisible. We tend to only notice it when it fails. If successful, it is stable and sustainable. Above all, it is trusted and relied on by the broad community it serves. Trust must run strongly across each of the following areas: running the infrastructure (governance), funding it (sustainability), and preserving community ownership of it (insurance)”.

These areas are fully define the Principles of Open Scholarly Infrastructure (POSI), which provide a set of guidelines by which open scholarly infrastructure organizations and initiatives that support the research community can be run and sustained.

As far as we are aware, Crossref was the first infrastructure to publish its compliance with POSI, detailed in Geoffrey Bilder’s December 2020 blog post

Crossref’s Board votes to adopt the Principles of Open Scholarly Infrastructure.

OpenCitations too espouses POSI and, in January 2021, we monitored the extent of our own compliance with POSI, the results of which are shown in the following diagram.

Governance

●	Coverage across the research enterprise	We gather citations from global scholarship
●	Stakeholder governed	Advisory board currently lacks executive power and is not elected
●	Non-discriminatory membership	Membership open to all those espousing open science
●	Transparent operations	Everything is open
●	Cannot lobby	OpenCitations lobbies to achieve open scholarly citations and bibliographic metadata; it does not engage in political or financial lobbying
●	Living will	Since all our data open, others can recreate our service
●	Formal incentives to fulfill mission & wind-down	No formal plan for wind-down has yet been drawn up

Sustainability

●	Time-limited funds used only for time-limited activities	Grant income should be used solely for grantprojects
●	Goal to generate surplus	Goal not yet realized – income so far too limited
●	Goal to create contingency fund to support operations for 12 months	Goal not yet realized – income so far too limited
●	Mission-consistent revenue generation	Membership fees and solicited donations
●	Revenue based on services, not data	All data and services freely given to community, and thus do not generate income

Insurance

●	Open source	All software under open source licenses
●	Open data	All data available under CC0 waiver
●	Available data	All data available via REST APIs, SPARQL endpoints, query interfaces and data dumps
●	Patent non-assertion	We will not patent anything: OpenCitations’ infrastructure is free to replicate

We at OpenCitations are proud of the results reached in the Insurance area, but realise that we still have some was to go in the other areas. Although the general situation is already satisfying, we are working to strengthen our weak points.

OpenCitations selected for SCOSS second funding cycle

The Global Sustainability Coalition for Open Science Services (SCOSS) is launching its second funding cycle, and OpenCitations is one of three open science infrastructure organizations whose services have been evaluated and selected for presentation to the international scholarly community for crowd-sourced sustainability funding, along with the Public Knowledge Project (PKP) and the Directory of Open Access Books (DOAB).

OpenCitations is an innovative infrastructure organization for open scholarship dedicated to the publication of open bibliographic and citation data concerning academic publications as Linked Open Data using Semantic Web technologies, thereby providing a disruptive alternative to traditional proprietary citation indexes. It also undertakes related advocacy work, particularly as a founding member of the Initiative for Open Citations (I4OC).

OpenCitations developed the OpenCitations Corpus (OCC), a database of open downloadable bibliographic and citation data recorded in RDF and released under a Creative Commons CC0 public domain waiver, which currently contains information about 14 million citation links to over 7.5 million cited resources. In addition and separately, OpenCitations is currently developing a number of Open Citation Indexes, using the data openly available in third-party bibliographic databases. The first and largest of these is COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations, which presently contains information encoded in RDF on more than 445 million citations, released under a CC0 waiver.

OpenCitations structures its data according to the OpenCitations Data Model (OCDM), that may also be employed by third parties, either for their own use or to structure their data for submission to and publication by OpenCitations. This model uses OpenCitations’ suite of SPAR (Semantic Publishing and Referencing) Ontologies developed to describe all aspects of the scholarly publishing domain. OpenCitations has also published open software of generic applicability for searching, browsing and providing REST APIs over RDF triplestores.

OpenCitations fully supports the founding principles of Open Science. It complies with the FAIR data principles proposed by Force11 that data should be findable, accessible, interoperable and re-usable, and it complies with the recommendations of I4OC that citation data, in particular, should be structured, separable and open. OpenCitations has published a formal definition of an open citation, and has launched a system for globally unique and persistent identifiers (PIDs) for bibliographic citations – the Open Citation Identifiers (OCIs) – for which it maintains an OCI resolution service.

OpenCitations has the potential to be a game-changer in the scholarly information landscape, giving institutions and individuals the ability to analyse and reuse publication citations in other infrastructures, in library collections, and in research. Open citation data are particularly valuable for bibliometric analysis, increasing the reproducibility of large-scale analyses by enabling the publication of the source data upon which analytical results are based. Since citation data are also crucial to evaluating research performance, such access to open, transparent citation data sources is a priority for Open Science.

SCOSS was formed in early 2017 with the purpose of providing a new coordinated and targeted crowd-sourcing and cost-sharing framework to enable the Open Access and Open Science communities to support the open infrastructure services on which they depend. In its first funding cycle, more than 1.5 million euros was pledged by more than 200 institutions worldwide to help fund and sustain the Directory of Open Access Journals (DOAJ) and SHERPA/RoMEO.

With the launch of its second funding cycle, SCOSS is appealing to academic institutions and their libraries, research institutes, publishers, funding organisations, national and regional governments, international organisations, learned societies and service providers worldwide — everyone who is invested in Open Access and Open Science — to support one or more of these three new selected open infrastructure services through a three-year commitment.

For more details about the services, suggested funding levels, and how you can help support OpenCitations, please see https://sparceurope.org/download/7913/ or contact us at [email protected].