Examples
Worked examples
- Is an instance
A query joining a Crossref DOI's authors via their ORCID iDs to their ROR-identified affiliations to their funded grants.
- Is an instance
DataCite Commons displaying linked people / works / organisations / funders for a single DOI.
Counter-examples
Looks similar, but isn't
- Not an instance
A standalone bibliography database with only internal IDs is not a PID graph.
- Not an instance
A relational table inside a single CRIS is not a PID graph.
- Not an instance
A single identifier crosswalk (one mapping between two schemes) is only one edge of a PID graph, not the graph itself.
Editorial commentary
The PID graph concept was promoted by DataCite, Crossref, and ORCID through the FREYA project (2017-2020) and is operationalised in services such as DataCite Commons, OpenAIRE Graph, and the OpenAlex aggregator. Each PID registry contributes edges based on the metadata it holds; the union forms a graph that supports queries such as ‘all outputs from authors affiliated with ROR X funded by funder Y’ that no single registry could answer alone.
Where the edges come from
No single provider builds a PID graph in isolation — it is assembled from many providers’ independently-held metadata, each contributing a slice: Crossref/DataCite deposit metadata contributes DOI-to-ORCID (authorship) and DOI-to-ROR (affiliation, via author metadata) edges; ORCID records contribute Person-to-Organisation (employment) and Person-to-Work edges; funder systems and grant metadata contribute funded-by edges. This is exactly why an identifier crosswalk — a single mapping asserting two identifiers refer to the same entity — matters: crosswalks are the mechanism that lets edges sourced from different registries actually connect into one graph rather than staying siloed by scheme.
Services built on the PID graph
DataCite Commons exposes the graph for any DataCite DOI, showing linked people, works, organisations, and funders. OpenAIRE Graph aggregates a broader European open-science-oriented view, harvesting CRIS systems, repositories, and PID providers together. OpenAlex builds its own large-scale scholarly graph substantially from PID-linked metadata (Crossref, ORCID, ROR) rather than web crawling.
References
- Fenner M., Aryani A., ‘Introducing the PID Graph’, DataCite blog (2019).
- FREYA Project, ‘Connecting Researchers and their Outputs through PIDs’ (project.freya-eu.org).
Also known as
Research graph · PID network
Machine-readable encodings
Use in your systems
<role vocab="credit"
vocab-identifier="https://casrai.org/dictionary/"
vocab-term="PID graph"
vocab-term-identifier="https://casrai.org/dictionary/term/pid-graph" />{
"@context": "https://schema.org",
"@type": "DefinedTerm",
"@id": "https://casrai.org/dictionary/term/pid-graph",
"name": "PID graph",
"identifier": "https://casrai.org/dictionary/term/pid-graph",
"description": "A graph data structure in which persistent identifiers (ORCID iDs, DOIs, ROR IDs, RAiDs, IGSNs, etc.) are nodes and the metadata relationships among them (creator-of, affiliated-with, funded-by, derived-from) are edges, allowing federated queries across multiple PID-provider registries.",
"inDefinedTermSet": "https://casrai.org/dictionary/domain/persistent-identifiers#set",
"url": "https://casrai.org/dictionary/term/pid-graph",
"sameAs": [
"Research graph",
"PID network"
],
"license": "https://creativecommons.org/licenses/by/4.0/",
"publisher": {
"@id": "https://casrai.org/#organization"
},
"author": {
"@id": "https://casrai.org/#editorial-team"
},
"datePublished": "2026-05-21T02:11:31",
"dateModified": "2026-08-22T15:38:20",
"inLanguage": "en-GB",
"isAccessibleForFree": true
}
