The Crossref Curriculum

Persistent identifiers

A persistent identifier (PID) is an ongoing, long-lasting digital reference to a resource. Digital object identifiers (DOIs) are persistent identifiers for entities such as journal articles, books, and datasets. You may have heard of ORCID iDs, which are persistent identifiers for researchers, Research Organization Registry IDs, and DataCite, which assigns DOIs for datasets. Crossref, ORCID, DataCite, and many other PID organizations work together to build trusted connections between DOIs, ORCID iDs, and other identifiers.

An identifier is a label which gives a unique name to an entity: a person, institution, or research work. Though a DOI is just a label, the value lies in its associated metadata, which is registered with the DOI and gives information about the work.

This metadata includes descriptive information about the work, administrative details such as the resource resolution URL, and structural information such as relationships to other research objects. Registering this metadata with Crossref makes it freely available to everyone in the scholarly community, making your work more discoverable.

When a work is published online, there’s no guarantee that the work will always be in the same place on the internet. The URL may change as publisher or hosting websites evolve, or the content might be acquired by a different publisher and be hosted on their site. If we refer to or cite a work using just the URL, this may not always go to the current location of the content, and we risk the work being lost from the scholarly record.

To keep the scholarly record persistent, we encourage publishers and scholars to use a persistent identifier to identify and cite works, rather than a URL. A Crossref DOI that you register with us is a persistent identifier for one of your works. If the resource resolution URL of the content changes in the future, you just update this information in the metadata, and the DOI will resolve to the new URL. That way, as long as scholars and publishers use a DOI to cite a work, they know they can reliably and accurately identify and find the work in the future.

A DOI becomes active once it and its metadata record have been registered with Crossref. Though the DOI doesn’t change, its associated metadata is kept up-to-date by the owner of the record.

PID map: identifying and linking research elements. We identify researchers using ORCID iDs, works using DOIs, research institutions using Organization IDs (ROR), and funders using Funder IDs. Grant IDs identify grants, and research equipment and materials. Having uniquely identified each element, we include relevant PIDs in the metadata of each element. The links show the relationships between the elements, and allow us to see how they are connected in time and space.

Learn more about the critical role of the DOI, the work of DataCite, ORCID and ORCID iDs, and the Research Organization Registry (ROR) and Research Organization Registry IDs.

DOIs are one of the most-used persistent identifiers in scholarly communication, and are used across disciplines. Read on to learn more about DOIs, their structures, and how to register them with Crossref.

Last Updated: 2020 April 8 by Laura J. Wilkinson