MEF (Multilingual Entity File) merges authority records from multiple national library sources into a single unified record per entity. The linking strategy differs by entity type — agents use VIAF as a central hub, while concepts and places rely on shared identifier codes embedded directly in the source records.
Agents
Persons · Organisations
Agent records from GND (Deutsche Nationalbibliothek), IdRef (Agence bibliographique de l’enseignement supérieur), and RERO (Réseau des bibliothèques de Suisse occidentale) are linked through VIAF (Virtual International Authority File) — an international hub that cross-references authority files from dozens of national libraries.
Each source record carries a VIAF source code inside its identifiedBy list. VIAF groups records from different sources that refer to the same person or organisation under a shared cluster. MEF harvests those VIAF clusters and uses the shared viaf_pid to merge the source records into one unified MEF record.
Source records connect to VIAF via their source code in identifiedBy. VIAF clusters matching records under a shared viaf_pid, which MEF uses to build one unified record.
Concepts
Topics · Subjects · Genres
Concept records from GND and IdRef are linked through a shared BNF identifier (Bibliothèque nationale de France). There is no external hub — the link key is embedded directly in the source records.
IdRef concept records carry a FRBNF* number in their identifiedBy list (type bf:Nbn); a heading that absorbed several BNF records keeps all of their numbers. GND concept records carry the same FRBNF* number inside their exactMatch entries. If no exactMatch entry contains a BNF identifier, MEF falls back to closeMatch. Whichever is used, all its entries must carry the same BNF number: when they carry different ones, the GND record is not linked, to avoid ambiguous links. MEF compares only the eight digits of the numbers (a trailing check character is ignored) to find and merge matching records. A BNF number carried by several records of a source links none of them, unless a single GND record carries it in an exactMatch entry.
RERO concept records are also included in MEF but do not carry a cross-source identifier, so they are not directly linked to GND or IdRef records.
IdRef and GND each embed the same FRBNF* BNF number in different fields. GND uses exactMatch entries, falling back to closeMatch; entries carrying different numbers give no link. MEF matches those codes across sources to link the records.
Places
Geographic locations
Place records from GND and IdRef are linked through the GND PID. RERO does not publish place authority data, so there is no RERO source for places.
GND place records serve as the anchor: their own pid is the link key. IdRef place records embed the corresponding GND PID (prefixed with (DE-101)) inside their identifiedBy list (source GND, type bf:Nbn). MEF strips the prefix and matches the bare PID to find the corresponding GND record. An IdRef record stating several different GND PIDs is not linked, nor are several IdRef records stating the same GND PID.
GND place records are the anchor. IdRef records carry the matching GND PID (with (DE-101) prefix) in identifiedBy.
Record redirects & lifecycle
How superseded records are tracked
Source authorities regularly merge or deprecate records. MEF tracks these changes through a relation_pid field on the source record embedded in each MEF record. The type depends on the source:
Source
Type
Meaning
GND
redirect_to
Old GND record (MARC 682 “Umlenkung”) points to its canonical replacement. The old record has its own MEF entry.
IdRef
redirect_from
Canonical IdRef record (MARC 035 sudoc) records the old SUDOC PID it replaced. The old PID may have no separate MEF entry.
The latest API endpoint resolves any source PID to the current MEF record:
Agents
/api/agents/mef/latest/<pid_type>:<pid>
Concepts
/api/concepts/mef/latest/<pid_type>:<pid>
Places
/api/places/mef/latest/<pid_type>:<pid>
Example: /api/agents/mef/latest/gnd:069774331 follows the redirect_to chain to return the current MEF record.
GND: old record A carries redirect_to: B and has its own MEF entry. /latest/gnd:A follows the redirect_to chain to reach the canonical MEF record. IdRef: canonical record B carries redirect_from: A. Old SUDOC PID A may have no separate MEF entry. /latest/idref:A finds B by searching for any record where idref.relation_pid.value = A.
