A persistent identifier (PID) is a long-lasting reference to a digital resource. Unlike URLs, which may break, a persistent identifier reliably points to a digital entity.
An ORCID iD is an example of a persistent identifier for a person. ORCID works closely with many other PID organizations to build trusted connections between ORCID iDs and other identifiers.
Persistent Work Identifiers
You may have heard of DOIs (digital object identifiers), which are persistent identifiers for things or entities such as journal articles, books, and datasets. Crossref and DataCite are examples of DOI registrars assigning DOIs for scholarly communication. ORCID supports DOIs, and many, many other PIDs that are used to identify scholarly outputs.
As well as identifying works contributed to, ORCID uses these PID types to identify peer review subjects, i.e. works that were reviewed.
Please see our list of supported identifiers for the V3.0 API. We occasionally add new types at the request of ORCID members who would like to use them when adding items to the registry.
Works in ORCID are grouped together based on both their identifiers and those identifiers‚ relationship to the work. There are four types of relationships:
- Self: the identifier refers solely to that work and can be grouped with other works that have the same identifier
- Part of: the work is part of this identifier and cannot be grouped with other works
- Version of: these identifiers apply to alternate versions of the work and can be grouped with self and version of identifiers
- Funded by: these identifiers apply to the funding for the work. These identifiers are not used for grouping works.
Our API provides support for this in the XSD. Each item has a display index attribute which indicates its rank within its group. The highest display index is the preferred item selected by the researcher, items added via the API which have not been ranked by the researcher have a display index of 0. The display index also determines the work order when reading the ORCID record.
For more information regarding grouping on ORCID records, please see our support article.
Persistent Identifiers normalization
In version 3 of the API, we apply some additional processing to normalize identifier values, so that they are comparable across systems.
We’ve introduced a new system-generated field, which expresses external identifiers (DOIs, PMCID, PMID, ArXiv, Bibcode, ISSNs, and ISBNs) in a normalized format for the purposes of matching and grouping. Normalization is done based on the rules of the identifier type, and may include setting all alpha characters to lowercase, or transforming spaces, dashes, periods and other characters that can be treated as equivalent. It also adds standard prefixes and suffixes as appropriate. For example, https://doi.org/10.1/123, 10.1/123, and https://dx.doi.org/10.1/123 will all appear in this field as https://doi.org/10.1/123. The existing identifier value is unmodified.
ORCID uses Organization Identifiers to disambiguate organizations in ORCID records, most often for Education and Employment affiliations.
Alongside work identifiers, ORCID has a long history of using ISSN identifiers. Since the very beginning it has been possible for researchers and ORCID members to associate Works with Journals using ISSN ids. ISSN IDs sit alongside other persistent identifiers, such as DOIs and Pubmed IDs within work metadata, and provide an unambiguous connection between the person, the work and the journal.
Peer review group identifiers
ORCID connects researchers with their peer review activity. This allows journals to acknowledge the huge amount of effort put in by researchers that might otherwise go unrecognised. Within the ORCID user interface and metadata, peer reviews are grouped together using persistent identifiers, usually ISSNs.
The ISSN portal has enabled ORCID to look up journal names at the authoritative source. We are using the openly available and machine readable ISSN data to display the name, along with a link to the portal landing page for that journal. This means that ORCID members deal with ISSN when managing their journal names. It means that the names we display are accurate, have a chain of provenance, and are up to date. And it means that individuals browsing the registry can discover more about the journals within records by visiting the ISSN portal directly.
Requesting new persistent identifiers
ORCID allows reference identifiers to be added to works, funding, and peer review items to help uniquely identify them within the ORCID Registry. The ORCID Registry also groups funding, works, and peer review items based on their associated unique identifier in both the user interface and API. We encourage anyone adding data to ORCID records to add as many identifiers as are known.
ORCID member organizations which exchange data via the ORCID API can request the addition of new external identifier types that all ORCID members and registrants can use to identify works. Requesting new identifiers is a benefit available only to ORCID members.
As a benefit of ORCID membership, organizations can ask ORCID to support additional PID types in the ORCID Registry. For example, a member could request that we add support for the PIDs they use for identifying samples or datasets in their geology database. This enables links between the samples and the people who collected them. And, because all new PID types that we add must be at least resolvable, and preferably FAIR, those links are unambiguous, persistent over time, and actionable – benefitting the researcher, the member organization, and the wider community.
Adding Your PID!
As a community organization, we want to ensure that ORCID supports the PIDs used by our members. We maintain a complete list of existing identifiers supported in the Registry and invite ORCID members to use this form to request additional PIDs. We aim to respond to your request as soon as possible.