Library of Congress Linked Data Service

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

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

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.
 * 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. All records are available individually via content negotiation as XHTML/RDFa, RDF/XML, N-Triples, and JSON.

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

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

Technical aspects
The id.loc.gov site initially used a fairly lightweight Python program to serve linked data.