Open Citations – Page 2 – OpenCitations blog

A technical overview of OpenCitations Meta

This blog post is the first of a series dedicated to the description and promotion of OpenCitations Meta.

In addition to OpenCitations’ Citation Indexes, OpenCitations is pleased to announce a new service: OpenCitations Meta, a database which stores and delivers bibliographic metadata for all publications involved in the OpenCitations citation indexes.

For each publication, the metadata exposed by OpenCitations Meta includes the publication’s title, type, venue (e.g. journal name), volume number, issue number, page numbers, publication date, and identifiers such as Digital Object Identifiers (DOIs) and PubMed Identifiers (PMIDs). In addition, OpenCitations Meta includes details of the main actors involved in the publication of the document, i.e., the names of the authors, editor, and publisher, each with its own additional metadata and identifier (e.g. ORCID).

Why OpenCitations Meta?

OpenCitations Meta represents a major infrastructural advance for OpenCitations, since it addresses and overcomes some of the limitations previously experienced, providing three major benefits:

1. It permits OpenCitations to respond more quickly to user requests for information.

The OpenCitations Citation Indexes contain citation-related metadata, such as the identifiers for the citing and cited publications, the citation timespan, and other citation-specific metadata, for example whether or not the citation is a self-citation. However, metadata for the citing and cited publications were hitherto not stored by OpenCitations, but rather obtained by on-the-fly API calls to external services such as Crossref, Datacite and ORCID. This dependence on responses from external services significantly slowed the delivery of the required information to users. Since OpenCitations Meta stores in-house the same bibliographic metadata for the citing and cited publications as was previously obtained by those external API calls, the former temporal limitation is now alleviated, thereby accelerating response times for requests made to the OpenCitations REST API services, and thus better supporting our users.

2. It permits OpenCitations to index citations involving publications that lack DOIs.

The second problem that OpenCitations Meta addresses goes beyond the OpenCitations infrastructure and addresses a more general issue of digital publishing, particularly in the Humanities, namely that many scholarly publications lack persistent identifiers such as DOIs and PMIDs. The citations indexed by OpenCitations are themselves treated as first-class data entities, each bearing a unique persistent Open Citation Identifier. According to the Open Citation Identifier definition [1], the entities linked by an indexed citation need to be identified by a persistent identifier (PID) from a recognised scheme such as the Digital Object Identifier scheme. For example, COCI [2] records the DOIs of the citing and cited entities. However, the association of DOIs with published documents is not uniformly spread across all scholarly fields. Indeed, in Scopus and the Web of Science Core Collection, only 50% of the current publications in the Art and Humanities are associated with a DOI [3]. In addition, in many fields, particularly in the Humanities, references are required to pre-digital historical primary sources that lack PIDs. OpenCitations Meta solves this problem by assigning a unique OpenCitations Meta Identifier (OMID) to each document. In this way, it can record the metadata of publications lacking an external identifier and store the citations involving them in one of the OpenCitations Indexes.

3. Use of the OpenCitations Meta Identifier permits de-duplication of records of bibliographic resources having more than one external identifier, such as a DOI and a PMID.

While many scholarly publications lack external PIDs, many others will have more than one external PID, for example a DOI for the record of that publication in Crossref, and a PMID for the record of that same publication in PubMed. This is perfectly legitimate. Since OpenCitations Meta assigns a unique OpenCitations Meta Identifier (OMID) to every entry, and in addition records all external identifiers already assigned to that publication, for example its DOI and its PMID, this permits the automatic de-duplication of such publications within OpenCitations Meta.

The data model

OpenCitations uses Semantic Web technologies to encode all its data, including the bibliographic metadata now stored in OpenCitations Meta. For this purpose, the OpenCitations Data Model (OCDM) [4] uses classes and properties defined in the SPAR Ontologies to represent:

bibliographic entities (fabio:Expression), e.g. a journal article
identifiers (datacite:Identifier), e.g. a DOI
agent roles (pro:RoleInTime), e.g. an author
responsible agents (foaf:Agent), e.g. a person
publication format details (fabio:Manifestation), e.g. first and last pages

Figure 1 depicts relationships between some of the various entities.

Figure 1. A small subset of the OCDM used in OC Meta. Yellow rectangles represent classes, green polygons represent data types, while blue and green arrows represent object properties and data properties, respectively

In addition to storing data, great importance is given to recording provenance and change-tracking of OpenCitations Meta entries, including the agent who processed a specific entity, i.e. creating, deleting, modifying or merging it, the date and time on which this action was performed, and the primary source of the data.

The data

At the release date, 20th December 2022, OpenCitations Meta is using Crossref as its primary source, with the purpose of hosting the metadata describing all citing and cited publications involved in the 1,392,036,835 citations within COCI [2]. From a quantitative point of view, OpenCitations Meta presently contains metadata describing 87,321,593 bibliographic entities, 277,750,235 authors, 2,359,301 editors, 17,268 publishers, and 710,226 publication venues (e.g. journal names). Editors and authors have been counted by their roles, without at this stage disambiguating individuals with the same name. Conversely, bibliographic entities, publishers, and publication venues were counted by their OMIDs. In total, the OpenCitations Meta triplestore presently contains 3,298,335,581 triples.

In the following days, OpenCitations Meta will be expanded to include bibliographic metadata for all citing and cited publications involved in the 169,822,752 citations from DataCite within DOCI, released on 13th December 2022.

Table 1 lists the various types of bibliographic resource represented in OpenCitations Meta. The current dataset contains mostly journal articles (60,683,841), which exceed the number of book chapters (6,288,351) by about ten times and the number of conference proceedings articles (4,917,568) by about twelve times.

Bibliographic resource type	Number of publications
journal article (fabio:JournalArticle)	60,683,841
book chapter (fabio:BookChapter)	6,288,351
proceedings article (fabio:ProceedingsPaper)	4,917,568
journal issue (fabio:JournalIssue)	4,340,894
book (fabio:Book)	3,138,154
journal volume (fabio:JournalVolume)	1,265,884
web content (fabio:WebContent)	285,962
reference book (fabio:ReferenceBook)	201,964
reference entry (fabio:ReferenceEntry)	184,515
dataset (fabio:DataFile)	156,343
report (fabio:ReportDocument)	153,864
journal (fabio:Journal)	133,963
proceedings (fabio:AcademicProceedings)	68,961
book series (fabio:BookSeries)	32,070
dissertation (fabio:Thesis)	20,226
standard (fabio:SpecificationDocument)	13,285
series (fabio:Series)	8546
book section (fabio:ExpressionCollection)	6754
peer review (fr:ReviewVersion)	4319
book part (doco:Part)	2474
book set (fabio:BookSet)	45

Table 1. All the bibliographic resources types involved in OpenCitations Meta, ordered by the number of publications of each type. The reference ontologies are FaBiO (http://purl.org/spar/fabio), DOCO (http://purl.org/spar/doco), and FAIR reviews (http://purl.org/spar/fr)

How to access the metadata in OpenCitations Meta

OpenCitations Meta allows the users to explore the contained metadata either via SPARQL (https://opencitations.net/meta/sparql) or via the OpenCitations Meta REST API (https://opencitations.net/meta/api/v1). In particular, the API will retrieve a list of bibliographic resources and related metadata starting from one or more identifiers including an OpenCitations Meta Identifier (OMID), an author’s ORCID, or an editor’s ORCID.

Finally, all the metadata and provenance information present in OpenCitations Meta are available as dumps in RDF (JSON-LD) or CSV format under a CC0 licence. Every time a citation index is updated, we will update OpenCitations Meta.

Conclusion

OpenCitations Meta makes search operations on the metadata of scholarly publications involved in the citations indexed in the OpenCitations Citation Indexes faster, since the metadata are now held in-house. The use of OpenCitations Meta Identifiers (OMIDs) permits OpenCitations Meta to act as a mapping hub to disambiguate and unify information on single publications identified by more than one external identifier, and makes it possible to characterise citations involving resources lacking an external identifier.

In the future, we will introduce a new API operation to perform text searches. Moreover, OpenCitations Meta will incorporate metadata from other sources in addition to Crossref. As mentioned above, work is already under way to ingest bibliographic metadata from Datacite for the publications involved in the citations newly indexed in DOCI. This will soon be followed with similar OpenCitations Meta entries relating to a new citation index, POCI, containing citations from PubMed, to be released later this year. PubMed metadata will be made available by February 2023.

References

Peroni, S. and Shotton, D. (2019). Open Citation Identifier: Definition. Figshare. https://doi.org/10.6084/m9.figshare.7127816
Heibi, I., Peroni, S. & Shotton, D. Software review: COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations. Scientometrics 121, 1213–1228 (2019). https://doi.org/10.1007/s11192-019-03217-6
Gorraiz, J., Melero-Fuentes, D., Gumpenberger, C., & Valderrama-Zurián, J.-C. (2016). Availability of digital object identifiers (DOIs) in Web of Science and Scopus. Journal of Informetrics, 10 (1), 98–10. https://doi.org/10.1016/j.joi.2015.11.008
Peroni, S. and Shotton, D. (2018). The OpenCitations Data Model. figshare. DOI: https://doi.org/10.6084/m9.figshare.3443876

Discover DOCI, the index of open citations from DataCite

We’re excited to introduce DOCI, the OpenCitations Index of Datacite open DOI-to-DOI citations, a new tool containing citations derived from publications bearing DataCite DOIs to other DOI-identified publications, harvested from DataCite. The citations available in DOCI are treated as first-class data entities, with accompanying properties including the citations timespan, modelled according to the OpenCitations Data Model.

Currently, DOCI’s December 2022 release contains 169,822,752 citations from 1,753,860 citing resources, and is based on the last dump of DataCite dated 22 October 2021 provided by the Internet Archive.

Citation URLs

Each citation (i.e. an individual of the class cito:Citation) is identified by an URL structured as follows:

https://w3id.org/oc/index/doci/ci/[[OCI]].

Open Citation Identifiers

Each Open Citation Identifier [[OCI]] has a simple structure: the lower-case letters “oci” followed by a colon, followed by two numbers separated by a dash (e.g. https://opencitations.net/index/doci/ci/080010504060836132137200707121027-080010504060836161221130313.html), in which the first number identifies the citing work and the second number identifies the cited work.

For citations in which the citing and cited works are identified by DOIs, which includes all the DOCI citations, the OCI is created in the following manner, as explained more fully here. Each case-insensitive DOI is first normalized to lower case letters. Then, after omitting the initial doi:10. prefix, the alphanumeric string of the DOI is converted reversibly to a pure numerical string using the simple two-numeral lookup table for numerals, lower case letters and other characters presented at https://github.com/opencitations/oci/blob/master/lookup.csv. Finally, each converted numeral is prefixes by a 080, which indicates that DataCite is the supplier of the original metadata of the citation (as indicated at http://opencitations.net/oci).

OCIs can be resolved using the OpenCitations OCI Resolution Service.

Access to DOCI data

All the data in DOCI:

can be queried by means of the OpenCitations Indexes SPARQL endpoint;
can be retrieved by using the DOCI REST API;
are available as dumps on Figshare in CSV, N-Triples and Scholix.

More information is available at https://opencitations.net/index/doci.

What is an Open Citation Index?

A citation index is a bibliographic index recording citations between publications, allowing the user to establish which later documents cite earlier documents. The current indexes available in OpenCitations are:

COCI, open citations from Crossref, available at http://opencitations.net/index/coci;
CROCI, the Crowdsourced Open Citations Index, available at http://opencitations.net/index/croci;
DOCI, open citations from DataCite, available at http://opencitations.net/index/doci .

All the OpenCitations Indexes have six characteristics in common, summarized here: https://opencitations.net/index

Follow OpenCitations on Mastodon

OpenCitations has happily joined the open-source social media platform joinmastodon.org.

Mastodon is “a free and open-source software developed by a non-profit organization”, with the aim of favouring interoperability and bringing social media interaction “back in the hands of the people”.

We look forward to recreating there our wide network of connections, and getting in touch with new people, projects and institutions in a different virtual environment.

Tutorial: how to process COCI’s zipped CSV dump without decompressing it

Blog post by Ivan Heibi (Universiy of Bologna) and Arcangelo Massari (University of Bologna).

OpenCitations publishes the COCI dataset after each new release in three main formats: CSV, N-Triples, and Scholix (see https://opencitations.net/download#coci). The CSV format is the most popular and downloaded one due to its comprehensive data organization (i.e. tabular format) and smaller size (compared to the other formats provided). Therefore, this is also the format we suggest using for a local process of the entire COCI dataset.

The CSV dumps of COCI are uploaded on Figshare. You can check and download the last dump released from https://doi.org/10.6084/m9.figshare.6741422. The dump consists of one main ZIP file, including other smaller ZIP archives (one for each release) containing the actual CSV files (Figure 1).

Figure 1. The contents of the COCI CSV dataset (after the August 2022 release)

It is possible to process this data without unzipping the internal archives, thus saving a lot of disk space. In this tutorial, we will see how to achieve this in Python. Same process could be done in other programming languages.

Processing the COCI dump using Python

Step 1) Downloading the COCI dump

First, you need to download the last CSV dump release of COCI from https://doi.org/10.6084/m9.figshare.6741422 and decompress only the external archive. After this operation, you should have a folder containing the internal ZIP files such as in Figure 1.

Note: It is beneficial to decompress the external archive because doing so does not increase the space occupied on the disk (compressing archives results in a compression rate of 0%) and because working on nested archives would significantly increase RAM requirements.

Step 2) Working with the ZIP files

Python provides the built-in zipfile module, whose ZipFile class allows you to create, read, write, edit and list the contents of a ZIP file. Given as input the path of the root directory containing all the ZIP files (FOLDER_PATH), the process elaborates each of these files on a different iteration. Each cycle initializes a ZipFile object by specifying the path to the ZIP file (archive_path).

from zipfile import ZipFile
import os

for archive_name in os.listdir(FOLDER_PATH):        
    archive_path = os.path.join(FOLDER_PATH, archive_name)
    with ZipFile(archive_path) as archive:
        # ...

Step 3) Accessing the ZIP files

Use the namelist() method to return the list of CSV files contained in each archive. Then to open the inner CSV files, simply cycle through the list of names and feed them to the open() method of the ZipFile instance, i.e. archive in the example below.

from zipfile import ZipFile
import os

for archive_name in os.listdir(FOLDER_PATH):
    archive_path = os.path.join(FOLDER_PATH, archive_name)
    with ZipFile(archive_path) as archive:
        for csv_name in archive.namelist():
            with archive.open(csv_name) as csv_file:
                # ...

Step 4) Reading the CSVs

The .open() method returns a buffer. To read the CSV file as a list of dictionaries (i.e. represent each row of the CSV in dictionary format, e.g., {“column1″:”val1”, “column2″:”val2”}) we need to transform the buffer using the TextIOWrapper class and read it using the DictReader class of csv. Then we convert the result of DictReader into a list.

from io import TextIOWrapper
from zipfile import ZipFile
import os

for archive_name in os.listdir(FOLDER_PATH):
    archive_path = os.path.join(FOLDER_PATH, archive_name)
    with ZipFile(archive_path) as archive:
        for csv_name in archive.namelist():
            with archive.open(csv_name) as csv_file:
                reader = csv.DictReader(io.TextIOWrapper(csv_file))
                rows = list(reader)
                # ...

Step 5) Processing the CSVs content

Now you can go through each row of the list and process the citation data as you want. The following example prints the citing and cited entity of each citation in the dump.

from io import TextIOWrapper
from zipfile import ZipFile
import os

for archive_name in os.listdir(FOLDER_PATH):
    archive_path = os.path.join(FOLDER_PATH, archive_name)
    with ZipFile(archive_path) as archive:
        for csv_name in archive.namelist():
            with archive.open(csv_name) as csv_file:
                reader = csv.DictReader(io.TextIOWrapper(csv_file))
                rows = list(reader)
                # Process the CSV here
                for r in rows:
                    print("Citing entity:",r["citing"])
                    print("Cited entity:",r["cited"])

Workshop on Open Citations and Open Scholarly Metadata – 5 October 2022

We’re happy to announce the 3rd edition of the Workshop on Open Citations and Open Scholarly Metadata (WOOC2022), to be held online on 5 October 2022 (h. 15-18 CEST).

It has now been two years since the last edition of the Workshop on Open Citations and Open Scholarly Metadata (WOOC2020) took place as an online event. During that event, the virtual format did not constrain an enriching and stimulating debate, fostered by the distinguished voices of the speakers involved.

In the past two years, the Open Science ecosystem has been enriched by growing infrastructures, new projects, and the increasing availability of open scholarly data. OpenCitations itself is now hosting over 1.36 billion open citations. We would like WOOC2022 to re-create a theme-focused virtual space to share updates, thresholds and challenges. Like the last event, WOOC2022 will take the form of a three-hour webinar for researchers, scholarly publishers, funders, policy makers, and opening citations advocates, interested in the creation, reuse, and improvement, of open citation data and open scholarly metadata, with speaker contributions followed by Q&A sessions. The workshop is organized around the following topics:

Reforming research assessment with open citations and open scholarly metadata;
Artificial intelligence to support the extraction and analysis of citations and metadata;
Sustainability of open science infrastructures;
Availability of open citations and open scholarly metadata in scholarly disciplines.

Participation

The participation is free of charge and requires no registration. The event will be live-streamed on OpenCitations YouTube channel and it will be possible to interact with the speakers through the YouTube live comments section during the streaming.

Program

During the Workshop on Open Citations and Open Scholarly Metadata, the talks of the distinguished speakers will be divided into four sessions, with one 5-minute break. At the beginning of the Workshop, OpenCitations director Silvio Peroni will acknowledge the selected author’s video contributions, whose links will be made available on the workshop website for engaging with interested parties and encouraging a broader discussion.

The programme is as follows:

Introduction

15:00 – 15:10 Silvio Peroni: Workshop Introduction and authors’ contribution acknowledgement

Session I

15:10 – 15.30 Victoria Moody: Lift, shift and re-use: Repurposing open access in new ways: The possibility (and probable necessity) of ensuring the capability and sustainability of research infrastructure assets through the enhanced deployment of open science approaches, creating new pathways for established approaches and extending their impact.

15:30- 15:50 Alberto Martín-Martín: Managing the scholarly record

Session II

15:50-16:10 Ludo Waltman: Let’s move beyond citations!

16:10- 16:30 Claudio Aspesi: Fixing scholarly communications may require moving beyond citations

5 min break

Session III

16:35- 16:55 Jennifer Lin and Ana-Maria Istrate: Essential frontiers: open data & software citations, an automated ML approach

16:55- 17:15 Philipp Mayr: Handling Non-source items in the project OUTCITE

Session IV

17:15- 17:35 Chiara Di Giambattista: Where were we? The role of the community in the present and future of OpenCitations

17:35-17:55 John Chodacki

17:55- 18:00 David Shotton: Roundup discussion and conclusion

Visit https://workshop-oc.github.io/ to read the talks’ abstracts and find more information about the Workshop on Open Citations and Open Scholarly Metadata.

All the workshop materials will be made available at

https://zenodo.org/communities/wooc2022/

List of invited speakers

Claudio Aspesi (Independent Consultant, Zurich, Switzerland)

John Chodacki (Director, University of California Curation Center)

Ana-Maria Istrate (Research Scientist, Chan Zuckerberg Initiative)

Jennifer Lin (Product Director, Indeed)

Alberto Martín-Martín (Assistant professor, Facultad de Comunicación y Documentación, Universidad de Granada)

Victoria Moody (Director of Research and innovation sector strategy, Jisc. Co-Investigator and Deputy Director, UK Data Service)

List of organizers

David Shotton (University of Oxford; OpenCitations)

Silvio Peroni (University of Bologna; OpenCitations)

Chiara Di Giambattista (University of Bologna; OpenCitations)

Ludo Waltman (Centre for Science and Technology Studies (CWTS), Leiden University; VOSViewer)

Philipp Mayr (GESIS – Leibniz-Institute for the Social Sciences; EXCite)

Giovanni Colavizza (University of Amsterdam; ScholarIndex)

Matteo Romanello (Swiss Federal Institute of Technology in Lausanne; ScholarIndex)

Follow the Workshop on Open Citations and Open Scholarly Metadata on Twitter:

Tweets by workshop_oc

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 Access Tokens: how they work and why they are important

Since its inauguration in 2010, OpenCitations has always granted free access to its services to users throughout the world, with no requirement for registration or sign-up. Programmatic access to OpenCitations data can be obtained either via our SPARQL endpoints and our REST APIs. In addition, OpenCitations data – available in CSV, Scholix, and RDF formats – can be downloaded from data dumps made periodically and stored on Figshare, so as to enable large-scale analyses using the whole content of the data sets, and also be obtained via our user-friendly text-based search and browsing interfaces.

One of OpenCitations’ priorities is (and will always be) to keep its data globally open and available at zero cost and without restriction for third-party analysis and re-use. As a matter of sustainability, OpenCitations relies on financial support from the scholarly community, which includes those institutions that use OpenCitations data. However, OpenCitations has not so far had in place a proper system to monitor its users, and the main evidence of the impact of OpenCitations in different academic fields and countries has been incompletely obtained from direct contacts with our members and donors across the world, our collaborations with international projects, and the interactions on our social platforms (Twitter and LinkedIn).

We would now like to institute a system that enables us to follow the usage and assess the impact of OpenCitations more reliably. For this purpose, we are now happy to announce the launch of the OpenCitations Access Token System for access to the OpenCitations data and services.

An OpenCitations Access Token is an opaque character string that anonymously identifies a unique user of the OpenCitations APIs. OpenCitations assigns an access token only if authorized to do so by each user, who can request a token by inserting his/her email address into the access form and clicking “Get token”. Upon submission of such a request, each user will automatically receive a personal access token by email. Users can save their personal access token and reuse it every time calling the APIs of OpenCitations, by passing it as a value for the key access-token in the header of each API call.

Obtaining and using an OpenCitations Access Token is thus easy. It only requires a simple form request, and then the insertion of your personal token into the API call header when using OpenCitations REST APIs. OpenCitations will not store users’ email addresses or any personal information, so that the users’ privacy will be totally safeguarded. The token system just provides a simple mechanism for identifying unique users, for which the use of IP addresses is insufficient.

Obtaining an OpenCitations Access Token will take the user only a few seconds and needs to happen only once. You can request your OpenCitations Access Token here:

https://opencitations.net/accesstoken

Use of an OpenCitations Access Token is not compulsory. However, token use will help OpenCitations incredibly, by enabling us to monitor the number of the unique users accessing our data and services, providing objective anonymized evidence of the number of institutions and researchers accessing our data either occasionally or on a regular basis, which we can then employ to demonstrate the usefulness of OpenCitations in the research environment. While the token system will initially be employed just for API calls (the most used service we offer), it will subsequently be extended to our other forms of data access.

OpenCitations exists for the people that use its data for research purposes every day, and thanks to their support. This is why obtaining precise knowledge of how many researchers and institutions are accessing our services is essential to us, since it will enable us to present the uniqueness and value of OpenCitations to new communities of stakeholders, and thus to make it possible to enlarge the already enthusiastic and diverse group of people and institutions supporting and using our Open Science Infrastructure.

To summarize: Getting and using an OpenCitations Access Token is voluntary, easy, and does not cost you anything. However, it will help OpenCitations a great deal. Please get your own token now, and use it next time you access OpenCitations. Thank you very much!

Additional 48 million citations in COCI, including references from IEEE

We announce the August 2022 release of COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations, which is based on open references to works with DOIs within the Crossref dump dated August 2022. This new release extends COCI with more than 48 million additional citations, giving a total number of more than 1.36 billion DOI-to-DOI citation links.

This release includes citations from the articles published over the last four years by IEEE, whose bibliographic references were opened in June 2022.

A fundamental role in pushing the commercial publishers to open their citation data was played by Crossref’s recent announcement to change its reference distribution policy, by making all its metadata open.

Besides IEEE, COCI already includes the citation data derived from Elsevier (open via Crossref since December 2020) and from the last articles published by the American Chemical Society (whose references were opened in February 2021)

You can find more information about COCI in our open-access article

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;
- can be retrieved by using the COCI REST API;
- can be searched by using the OpenCitations Indexes Search Interface;
- are also available as dumps on Figshare in CSV, N-Triples, and Scholix; and
- can be freely re-used for any purpose.

New documents that present OpenCitations’ mission, unique benefits, present status and future plans

Posted on August 10th 2022 by Chiara Di Giambattista

More than a year ago, Ginny Hendricks, Director of Member & Community Outreach for Crossref, and a valued member of the OpenCitations International Advisory Board, published on the Crossref blog the post “The road ahead: our strategy through 2025”. In order to describe all Crossref’s principles and activities, Ginny presented the Crossref strategic planning framework as a diagram summarizing Crossref’s statements, key messages and truths. The clarity and immediacy of the diagram were such that we adapted it to present OpenCitations’ own statements and goals. The resulting poster “OpenCitations – what does the future hold?” was presented by our Director David Shotton at the OASPA2021 conference, and can be found in this blog post.

Although the poster offered a wide overview of OpenCitations values, unique traits, benefits and plans, it differed slightly from Ginny’s original diagram, in particular because it lacked a “Mission Statement”, scattering the relevant information within the “Values” and “Principles” boxes. Indeed, at that time (September 2021), we didn’t have a clearly defined Mission Statement.

Nevertheless, the creation of that poster was crucial in helping us start to articulate more clearly the purpose and meaning of OpenCitations. As David underlined in his post “From little acorns…a retrospective on OpenCitations”, since 2018 OpenCitations activities have progressively increased and, with them, the number of related journal articles, conference papers and technical definitions. OpenCitations’ involvement in international networks and collaborations (such as SCOSS and the OpenAIRE-Nexus project), together with our need of identifying and reaching out to new stakeholders to assure OpenCitations’ development and sustainability, has made it necessary to publicly define OpenCitations’ mission, unique strengths and next developmental steps.

After numerous revisions, aided by wise advice from members of the OpenCitations Advisory Board members, we’re now happy to publish the following three OpenCitations documents:

OpenCitations Mission Statement,

The Uniqueness of OpenCitations and

OpenCitations – Present Status and Future Plans,

which together provide a summary of why we exist and where we are heading.

We are particularly proud of the definition of OpenCitations’ primary mission, namely

“to harvest and openly publish accurate and comprehensive metadata describing the world’s academic publications and the scholarly citations that link them, and to preserve ongoing access to this information by secure archiving.”

The Mission Statement also presents brief descriptions of the OpenCitations context, our vision, our value proposition and our relationship with the community and stakeholders.

The Uniqueness of OpenCitations provides the answer to the question ‘Why choose to use OpenCitations?’, and is a detailed presentation of OpenCitations’ benefits.

OpenCitations – Present Status and Future Plans summarizes OpenCitations’ ongoing activities, that can be quickly visualized on our public roadmap. It also introduces the OpenCitations Working Groups, served by the members of the OpenCitations International Advisory Board, which are currently working on the themes of governance evolution and community building, with the common purpose of driving OpenCitations along the path from being a ‘sustainable infrastructure’ (in POSI terms) to being an enduring community led and financially sustained infrastructure.

In fulfilling our mission and reaching our goals, the support and vital interest of our community members is fundamental. We request that you, as a member of our community, provide us with feedback on these documents and the ideas they contain, or indeed to ask for clarifications, to help us improving our mission and our communications to explain it. You can reach us here: contact@opencitations.net.

Thank you!

Two years of achievements within the ‘SCOSS family’ (and it’s not over yet!)

Posted on August 10th 2022 by Chiara Di Giambattista

← Previous post: The OpenCitations Roadmap is now publicly available on Trello

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In March, The Global Sustainability Coalition for Open Science Services (SCOSS) celebrated, together with the generous funders and the projects involved (including OpenCitations), the achievement of an amazing milestone: a total of 4 million Euros raised so far for supporting the growth and development of Open Science Infrastructures. This significant sum is not just a number, but a concrete sign of the commitment of numerous institutions all over the world to ensure the success of vital organs of the Open Science ecosystem. Thanks to the pledges recently made, the new infrastructures selected for the third SCOSS pledging round have now started developing their services and can now look to the future with more surety.

At the end of 2019, OpenCitations was selected by SCOSS for its second pledging round, and since then much progress has been made. As the OpenCitations’ founder and director David Shotton recently stated:

“OpenCitations is growing, thanks to the generous support from our members and donors, and we thank SCOSS sincerely for bringing us into contact with them. The citation coverage provided by OpenCitations is now approaching parity with that of the leading commercial citation indexes, and our ambition, within the next five years, is for OpenCitations to be routinely used by our worldwide stakeholders as their primary source of comprehensive scholarly citation information”.

In 2020, OpenCitations monitored the achievements of the first year of SCOSS support and shared the most important updates in a blog post. After a review from SCOSS Advisory Group and the SCOSS Board, the OpenCitations 2021 report to SCOSS is now available in the SCOSS May newsletter. We’re proud of the successful developments that 2021 brought with it in many areas, from the technical enhancements to OpenCitations to its new supporters and partnerships.

After a two-year-long collaboration, we in OpenCitations recognise that one of the most precious benefits of being part of SCOSS is working within a community: SCOSS not only provides a framework but also a real family of supportive institutions that support the Infrastructures during their growth and provide a safety net if troubles occur along the path. The bi-monthly meetings organized by the SCOSS team enable dialogue with the other infrastructures within the same pledging round, while presentation and promotion to the institutions worldwide are fostered by participation in webinars and conferences. During 2021, OpenCitations participated in 16 events, and in 5 of them (LIBER Webinar 2021, JISC Webinar 2021, LIBER Annual Conference 2021, Open Science Fair 2021, and Open Access Tage 2021) OpenCitations’ director Silvio Peroni gave talks together with the representatives of others infrastructures involved in the SCOSS second pledging round.

In compliance with the POSI principles, SCOSS encouraged OpenCitations to set up an open governance structure. As described here, the organizational bodies included in the OpenCitations present governance are three: the Directors, the International Advisory Board, and the Council. Although executive power is still currently vested in the hands of the Directors, in the last two years the OpenCitations International Advisory Board, a committee that now comprises nine Open Science experts from different professional and academic backgrounds, has had a crucial role in guiding the OpenCitations activities, and it is now working on strategic developments in terms of collaborations, policies, support and governance. Moreover, last December OpenCitations organized a Webinar in conjunction with its Annual Meeting to present and discuss with the OpenCitations Council members OpenCitations’ recent developments and future plans.

OpenCitations is highly reliant upon the connections we have created and on people working together: thanks to the support we received throughout the last two years, the OpenCitations team has grown and now includes six people employed by the Research Centre for Open Scholarly Metadata at the University of Bologna, the administrative body for OpenCitations. Besides the previously announced appointments of Claudio Fabbri (Research Manager), Chiara Di Giambattista (Communications Director and Community Development Manager), Giuseppe Grieco (Software and Systems Developer), and Arcangelo Massari (Software Developer, working within the OpenAIRE-Nexus project), early in 2022 Ivan Heibi, Ph.D. candidate at the University of Bologna, joined OpenCitations with responsibility for the technical infrastructure, and Arianna Moretti, who recently graduated in Digital Humanities and Digital Knowledge, joined as a software developer. This enlarged team, involving young and motivated researchers, is working on numerous projects to be announced later in 2022. You can learn more about OpenCitations’ ongoing activities on our public roadmap.

OpenCitations’ aim continues to be the publication of open data describing the bibliographic citations linking global scholarly publications, with depth and scope, while maintaining the highest standards of accuracy and provenance. Most importantly, OpenCitations services will always be free, making global scholarly citation data available at zero cost and without restriction for third party analysis and re-use.

With its support, SCOSS has been helping OpenCitations to pursue its mission and spread the benefits of Open Science. However, 2022 will be the last year of the three-year-long support ensured by SCOSS. OpenCitations activities won’t stop in 2023 — indeed there still are many long-planned activities that we hope to initiate in the near future, given sufficient resources. This is why OpenCitations requires ongoing support from the scholarly community. All the information you may require to start helping us financially is available on the OpenCitations website: https://opencitations.net/membership

By supporting OpenCitations, you will embrace and sustain the ideals and vision of Open Science, and you will help in creating a more open, democratic and fair knowledge environment.