ORCID allows reference IDs to be added to works, funding items, or to works for which a peer review activity was performed (the review subject), to help uniquely identify them within the ORCID Registry.
Current versions of the ORCID schema support identifiers directly related to the item as well as identifiers for parent child items. Identifiers for child items should not be included at this time. The relationship between an identifier and a work, funding, or review subject can be one of two types:
- Self: The item identifier, e.g. the DOI of a book chapter
- Part of: The parent identifier, e.g. the ISBN of a book of which the work is one chapter
- Version of: The item identifier used to indicate that one work is a version of another. e.g. to relate multiple versions of a dataset together, or to group preprints with the published version of a paper
The ORCID Registry checks for duplicates by identifier and "self" relationship, and two items from the same client integration with the same identifier and "self" relationship cannot be added to a single ORCID record.
A complete list of used identifiers on the ORCID Registry can be found by querying the identifiers API.