The LC Linked Data Service is an initiative of the Library of Congress that publishes authority data as linked data.^[1] It is commonly referred to by its URI: id.loc.gov.^[2]

The first offering of the LC Linked Data Service was the Library of Congress Subject Headings (LCSH) dataset, which was released in April 2009.^[3]

Datasets

• Library of Congress Subject Headings (LCSH)
• Library of Congress Name Authority File (LCNAF)
• Library of Congress Classification—because LC Classification uses a different MARC format than LC Authorities, mapping LC Classification to MADS/RDF was more difficult than mapping LCSH or LCNAF.^[2]
• Library of Congress Thesaurus for Graphic Materials
• Various MARC codes
• Various preservation vocabularies

Formats

The service presents data in MADS/RDF and SKOS where appropriate, but also uses its own ontology to describe classification resources and relationships more accurately.^[2] All records are available individually via content negotiation as XHTML/RDFa, RDF/XML, N-Triples, and JSON.^[4]

Each vocabulary is also available to download in its entirety. Id.loc.gov does not currently provide a SPARQL endpoint.^[5][6]

Uses

All of LCSH are crosslinked with RAMEAU [d] (Répertoire d’autorité-matière encyclopédique et alphabétique unifié), an authority file from the Bibliothèque nationale de France.^[4]

Technical aspects

The id.loc.gov site initially used a fairly lightweight Python program to serve linked data.^[5]