Subject Schemes contains a list of subject schemes and assigns a URI to each scheme. The purpose of these properties is to permit users to associate controlled subjects with the appropriate subject scheme.

These schemes are general subject heading and thesauri, such as the Library of Congress Subject Headings, along with a number of focused subject term lists like Medical Subject Headings or Getty Thesaurus of Geographic Names. Additional specialized lists are provided with source codes in

• Genre/Form Schemes
• Occupation Term Source Codes
• Function Term Source Codes
• Temporal Term Source Codes

Since general thesauri often contain a broad spectrum of terms, including genre, forms, occupations, functions, and time periods, the source codes in this list may be used in the metadata elements identified for each of the specialized source lists.

Some subject heading lists incorporate names and titles and others employ independent name and title lists for parts of a subject heading. Thus the lists assigned source codes in Name and Title Source Codes may also be used in the metadata elements identified.

Classification schemes and subject category codes include caption terms and, frequently, index terms that identify the classes in the scheme and the category codes. Some systems use those caption and index terms as subject terms in bibliographic data. Thus the lists assigned source codes in Classification Schemes and Subject Category Code Source Codes may also be used in the metadata elements identified, when the terms from those classification schemes and subject category codes are used as subject terms.

Entries in the list may include the bibliographic citation for the source documentation. The citations are linked to the online source for some codes. In some cases those citation links are RDF resources.

Each code consists of a maximum of 12 lowercase alphabetic characters. Possible additions to codes are described in Source Codes .