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.

ByCASRAI Editorial Board

· Last updated 10 Jul 2026

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.

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.

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

JATS XML <role> element

xml

<role vocab="credit"
      vocab-identifier="https://casrai.org/dictionary/"
      vocab-term="PID graph"
      vocab-term-identifier="https://casrai.org/dictionary/term/pid-graph" />

Schema.org DefinedTerm (JSON-LD)

json

{
  "@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"
  },
  "dateModified": "2026-07-10T02:06:20",
  "inLanguage": "en"
}

Referenced across the research world

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