Although it is generally not necessary to convert a library's classification from one actively maintained system to another--and both LC and Dewey are continuously updated to reflect current topics and publishing--it is also sometimes useful to have a road map from one to another. There are printed conversion tables, as well as online versions.
Adding subject headings, selected from a controlled vocabulary, to a catalog record allows the catalog user to retrieve all items on a given subject in a consistent manner.
There are two controlled vocabularies commonly used in libraries:
Library of Congress Subject Headings (LCSH) were developed and are maintained by the U.S. Library of Congress, initially for the collections of the Library. LCSH, as a controlled vocabulary used for indexing, cataloging, and searching for bibliographic records in library catalogs and electronic databases, has become a de facto standard for libraries who use cataloging records disseminated by the Library of Congress, or who catalog to the standards set collaboratively by the Library of Congress and the library community. LCSH is updated daily in Classification Web.
Sears List of Subject Headings, first published by Minnie Earl Sears in 1923, has served as a standard authority list for subject cataloging in small and medium-sized libraries, delivering a basic list of essential headings, together with patterns and examples to guide the cataloger in creating further headings as needed. It is available as a print publication and an online database.
Other controlled vocabularies in use with library materials:
Faceted Application of Subject Terminology (FAST) is an adaptation of the Library of Congress Subject Headings with a simplified syntax. The purpose of adapting the LCSH with a simplified syntax to create FAST is to retain the very rich vocabulary of LCSH while making the schema easier to understand, control, apply, and use. The schema maintains upward compatibility with LCSH, and any valid set of LC subject headings can be converted to FAST headings.
BISAC Subject Codes List, or BISAC Subject Headings List, has been developed by the Book Industry Study Group as an industry-approved list of subject descriptors, each of which is represented by a nine-character alphanumeric code, was developed to standardize the electronic transfer of subject information. The headings can be used for transmitting information between trading partners, as search terms in bibliographic databases, as access points for database searching and as shelving guides. Many businesses require that publishers use BISAC Subject Headings when submitting data for all formats (physical and digital). Many businesses and most major publishers within the North American book industry use the headings in a variety of ways.