Documentation

h1. OpenAIRE entity identifier and PID mapping policy

(copied from https://docs.google.com/document/d/1PnvZpmhbanJu3AeOT-zdIyMKIHoGKC4_Z0UtDFDZAeM/edit#)

OpenAIRE assign internal identifiers for each object it collects. 

By default, the internal identifier is generated as @sourcePrefix::md5(localId)@ where 

* @sourcePrefix@ is a namespace prefix of 12 chars assigned to the data source at registration time

* @localid@ is the identifier assigned to the object by the data source

After years of operation, we can say that:

* @localId@ are unstable

* objects can disappear from sources

* PIDs provided by sources that are not PID agencies (authoritative sources for a specific type of PID) are often wrong (e.g. pre-print with the DOI of the published version, DOIs with typos)

Therefore, when the record is collected from an authoritative source:

* the identity of the record is forged using the PID, like @pidTypePrefix::md5(lowercase(doi))@

* the PID is added in a @pid@ element of the data model.

When the record is collected from a source which is not authoritative for any type of PID:

* the identity of the record is forged as usual using the local identifier;

* the PID, if available, is added as @alternateIdentifier@s

As of November 2021, the following data sources are used as "PID authorities": 

| PID Type | Prefix (12 chars) | Authority |

| doi | @doi_________@ | Crossref, Datacite, Zenodo |

| pmc | @pmc_________@ | Europe PubMed Central, PubMed Central |

| pmid | @pmid________@ | Europe PubMed Central, PubMed Central |

| arXiv | @arXiv_______@ | arXiv.org e-Print Archive |

| handle | @handle______@ | any repository |

TODO: WHAT HAPPENS FOR RECORDS WITH BOTH pmc and pmid? pmc wins?

OpenAIRE also perform duplicate identification (see dedicated section for details).

All duplicates are "merged" together in a "representative record" which must be assigned to a dedicated OpenAIRE identifier (i.e. it cannot have the identifier of one of the aggregated record).

The following strategy is applied to generate the OpenAIRE identifier of a representative record, to ensure it is as stable as possible:

TODO