Specify the data values or terminology to be used within given elements, categories or fields, in order to facilitate retrieval. Examples include thesauri, controlled vocabularies and authority files.

• Canadian Subject Headings (CSH) - list of standard subject headings on Canadian topics, which complements Library of Congress Subject Headings (LCSH) and is compatible with LCSH in its underlying principles
• Data Documentation Initiative (DDI) - project to develop an XML document type definition for data documentation
• Dictionary of Occupational Titles
• Getty Information Institute: Vocabularies
• Global Legal Information Network (GLIN) Subject Headings - used for The Global Legal Information Network's multi-national database of legislation has been under continuous development since 1950
• ISAAR - CPF (Corporate Bodies Persons and Families)
• Legislative Indexing Vocabulary (LIV) - especially developed for use with legislative and public policy subject matter, legislative analysts from the Congressional Research Service (CRS) of the Library of Congress examine the content of each bill and assign one or more index (subject) terms to each bill
• Library of Congress Name Authority File (NAF) - enumerates the preferred form of personal and corporate names, and provides links to alternative and variant forms of names, as well as pseudonyms
• Library of Congress Subject Headings (LCSH) - topical headings that describe the content or subjects of books and archival materials
• Linking And Exploring Authority Files (LEAF) - developing a model architecture for a distributed search system harvesting existing name authority information aiming at automatically establishing a user needs based common name authority file in a specific sector highly relevant to the cultural heritage of Europe
• Medical Subject Headings (MeSH) - controlled vocabulary used for indexing articles, for cataloging books and other holdings, and for searching MeSH-indexed databases, including MEDLINE
• Resource Description Framework (RDF)
• Revised Nomenclature for Museum Cataloging
• Rules for the Construction of Personal, Place and Corporate Names - National Council on Archives
• Union List of Artists Names (ULAN) - authority data for the names of artists. Alternatives, spelling variants, nicknames, and pseudonyms for an individual are clustered so that a preferred form may be chosen. Entries also include biographical data (e.g., life dates, role) and bibliographic citations referring to the artist.