Subject indexing schemes provide controlled access to the content of resources. Schemes define concepts and relationships between concepts to support user navigation.

The Library of Congress Subject Headings have been maintained by Library of Congress since 1898,  and are used for cooperative cataloguing around the United States as well as internationally, often in translation.

Well-known national subject indexing schemes include:

  • The French scheme RAMEAU (Répertoire d'autorité-matière encyclopédique et alphabétique unifié)
  • The 2006 published Italian system Nuovo Soggettario
  • The Canadian French language scheme RVM (Répertoire des vedettes-matière de la Bibliothèque de l'Université Laval)