Digital object identifier: The DOI

Have you ever thought about the alphanumeric link often at the end of a reference? What is the purpose of this, and why is it now required with references to journal articles in most reference styles? That alphanumeric link is called a digital object identifier, or DOI, and it may be the most important part of the reference for discovering, managing, and linking scholarly content and objects. The DOI is a unique alphanumeric string assigned to articles and other scholarly content that exist wholly or partially in a digital form. DOIs act similarly to URLs or weblinks yet differ in persistence, stability, and interoperability with a range of metadata schema. DOIs are applied to scholarly content or objects by a registrant-assigner (typically a publisher or research organization) via forms created and managed by the International DOI Foundation (IDF) (https://www.doi.org/) and registering agencies. Adoption of the DOI as a required or highly recommended addition to references has grown globally with many world regions seeking to join this growth and benefit from DOI use.1, 2 DOI development and implementation began in the late 1990s to early 2000s.3 Born-digital content (e.g., articles published digitally before or instead of in print) may be assigned a DOI as a matter of course with older materials retroactively receiving DOIs as they are cited or digitized. The addition of the DOI as a metadata field allows users to reach the homepage of a given article, dataset, or other object from database pages (such PubMed or CINAHL), article reference lists, and other digital locations with a click on the link. Of note, articles in Nurse Author & Editor are now considered “born-digital content” with the transition to the Wiley Online Library in the summer of 2021. Older articles from the Nurse Author & Editor have all been assigned DOIs retroactively. DOI as links are intended to provide a persistent identifier for an individual object such as an article or dataset regardless of its digital location. In other words, if a webpage or URL of a scholarly object changes, the DOI will remain consistent, and the scholarly work associated with the DOI can still be found with minimal searching. In the increasingly fast-paced world of nursing research and publication, quickly and effectively locating sources through references is a boon. Nursing scholars have noted the value of DOI usage for increased discoverability, management, and interlinking scholarly communications and sources.4-6 In addition to following DOI links, reference management software programs, such as Zotero, have integrated retrieval features that automatically search and retrieve one or a list of articles based on the DOI (see Figure 1). By copy-pasting a DOI from a reference, the search engine can automatically retrieve the associated content. Zotero's digital object identifier retrieval feature Several registering agencies facilitate DOI infrastructure and services—frequently dependent on the material type of the digital object or by geographic region.6, 7 Though the majority of material types may be textual, datasets, physical objects, and non-article born-digital materials (e.g., Git code) may also have DOIs assigned to them. The IDF manages the DOI® System and is a non-profit membership organization that governs the federation of registration agencies providing DOI services and registration. Standardization of DOI systems, to which the IDF adheres, including creation, is provided by the International Standardization Organization (ISO) in ISO 26324:2012 (https://www.iso.org/standard/43506.html). The System provides an infrastructure for the registration of persistent identifiers to be used in linking digital content such as scholarly articles. Research and other organizations wishing to participate in the DOI system apply for an account with an agency. With their membership, they are assigned a DOI prefix unique to their organization distinguishing their scholarly outputs from other organizations. The System currently includes over 5,000 assigners who have assigned over 257 million DOIs with 150,000 unique prefixes.3 The format of DOIs has changed somewhat over time.6 The DOI System uses a consistent format, much like the barcoding system. DOI numbers begin with a 10 and contain a prefix and a suffix separated by a slash.8 The prefix is a unique number of four or more digits assigned to organizations with the suffix being assigned by the publisher (See Figure 2). This is designed to be flexible with publisher identification standards. Handle system Crossref (Lynnfield) was developed early as a registering agency and is perhaps the most widely known. Its purpose is to enable cross publication reference linking for academic online journals. A detailed discussion of DOI registration agencies is beyond the scope of this article, but we will use Crossref as an example to discuss the benefits that such membership can provide. Content publishers become members of Crossref so that they can create a specific DOI, or persistent identifier, and then register content. Using metadata, the content from a member journal is then connected with a global network. Membership in this organization extends beyond scholarly journals and is open to any organization that produces scholarly content, such as government agencies, research funders, or museums. In addition to increasing the discoverability of their content, members can also participate in the governance of the organization. There are other services that can register funders, check for plagiarism, and provide reports about DOI conflicts or errors.9 Cross-linking of references is of benefit to readers because they can use the direct link provided by the DOI on a reference list for immediate access to referenced content. This link is included as a URL at the conclusion of the reference. The Crossref website notes that the increase of online content has led to the expectation by researchers and others that they can perform a simple click on a reference citation to find the cited content. The common infrastructure that this agency provides with the use of a persistent identifier increases the longevity of a working link, although this also depends on members updating information as appropriate.10 The Crossref website explains that different types of metadata can be used for different purposes. Listed are discoverability; research and editorial integrity; reproducibility; and reporting and assessment, with examples of each metadata element type.11 Registration of content through membership in an agency such as Crossref significantly increases the persistence and reach of scholarly content to the benefit of both publishers and consumers. It also increases the efficiency for readers with the ability to connect quickly and directly to referenced content. In addition to Crossref, several other registering agencies provide DOI infrastructure for articles and other scholarly content. Many registering agency missions and objectives overlap. Similar to Crossref but focused on data, DataCite (https://datacite.org; Hannover, Germany) provides DOIs for datasets allowing the data to be linked to the article it supports. Very recently, Earth sciences and data professionals have begun to explore assigning DOIs to research instruments (e.g., laboratory instruments).12 New identifiers such as the Research Resource Identifier via SciCrunch (https://scicrunch.org; FAIR Data Informatics Lab) for instruments and materials (e.g., cell samples) have also developed. Assigning persistent identifiers to datasets and instruments as well as articles may increase the reproducibility and transparency of research, particularly when instruments, created data, and resulting articles are intuitively interlinked. For this reason, some research university and organizational libraries have begun to facilitate DOI assignment to open-access manuscripts, datasets, and other scholarly content via their institutional repositories.13 These services are often accompanied by expertise to adapt DOI infrastructures to new and innovative scholarly needs and content. Within nursing and health research, the ability to efficiently discover and reuse pre-existing data and accurately identify research instrument details may increase the precision and reduce the research waste involved in data-driven and technological research. Effective use of DOIs requires an understanding of the systems and structures that provide DOI services and potential pitfalls as well as benefits. For editors and peer-reviewers, it is important to examine and correct any misformatted or inaccurate DOI links in reference lists. Scholars and authors should cultivate on awareness of DOI (and other persistent identifiers) best practices. Educators should do likewise with the goal of aiding learners and future scholars in best practices including recognizing that DOIs are not signifiers of quality and emphasizing the need to evaluate literature regardless of DOI presence. Heather Carter-Templeton, PhD, RN-BC, FAAN is Chairperson, of the Adult Health Department and an Associate Professor at West Virginia University, School of Nursing in Morgantown, WV. She is also the ANI Connections Editor for CIN: Computers, Informatics, Nursing. Contact Heather by email at: [email protected]. Jordan Wrigley, MSLS, MA is a data scientist and librarian with the Center for Research Data and Digital Scholarship (CRDDS) at the University of Colorado – Boulder. She is a contributing editor focused on data in information and library sciences for The Librarian Parlor. Email: [email protected]. Jacqueline K. Owens, PhD, RN, CNE is a professor of nursing at Ashland University Schar College of Nursing and Health Sciences in Ashland, OH. She is Editor-in-Chief of OJIN: The Online Journal of Issues in Nursing. Her email is [email protected] Marilyn H. Oermann, PhD, RN, ANEF, FAAN, is Thelma M. Ingles Professor of Nursing, Duke University School of Nursing, Durham, North Carolina, USA. She is Editor-in-Chief of Nurse Educator and the Journal of Nursing Care Quality. Email: [email protected]