Dataset Descriptions

Library of Congress Subject Headings (LCSH) has been actively maintained since 1898 to catalog materials held at the Library of Congress. By virtue of cooperative cataloging other libraries around the United States also use LCSH to provide subject access to their collections. In addition LCSH is used internationally, often in translation. LCSH in this service includes all Library of Congress Subject Headings, free-floating subdivisions (topical and form), Genre/Form headings, Children's (AC) headings, and validation strings* for which authority records have been created. The content includes a few name headings (personal and corporate), such as William Shakespeare, Jesus Christ, and Harvard University, and geographic headings that are added to LCSH as they are needed to establish subdivisions, provide a pattern for subdivision practice, or provide reference structure for other terms. This content is expanded beyond the print issue of LCSH (the "red books") with inclusion of validation strings.

*Validation strings: Some authority records are for headings that have been built by adding subdivisions. These records are the result of an ongoing project to programmatically create authority records for valid subject strings from subject heading strings found in bibliographic records. The authority records for these subject strings were created so the entire string could be machine-validated. The strings do not have broader, narrower, or related terms.

The Library of Congress Name Authority File (NAF) file provides authoritative data for names of persons, organizations, events, places, and titles. Its purpose is the identification of these entities and, through the use of such controlled vocabulary, to provide uniform access to bibliographic resources. Names descriptions also provide access to a controlled form of name through references from unused forms, e.g. a search under: Snodgrass, Quintus Curtius, 1835-1910 will lead users to the authoritative name for Mark Twain, which is, "Twain, Mark, 1835-1910." Names may also be used as subjects in bibliographic descriptions, so they may be combined with controlled values from subject heading schemes, such as LCSH.

Library of Congress Names includes over 8 million descriptions created over many decades and according to different cataloging policies. LC Names is officially called the NACO Authority File and is a cooperative effort in which participants follow a common set of standards and guidelines.

The Library of Congress Classification (LCC) is a classification system that was first developed in the late nineteenth and early twentieth centuries to organize and arrange the book collections of the Library of Congress. Over the course of the twentieth century, the system was adopted for use by other libraries as well, especially large academic libraries in the United States. It is currently one of the most widely used library classification systems in the world.

The system divides all knowledge into twenty-one basic classes, each identified by a single letter of the alphabet. Most of these alphabetical classes are further divided into more specific subclasses, identified by two-letter, or occasionally three-letter, combinations. For example, class N, Arti>, has subclasses NA, Architecturei>; NB, Sculpturei>, ND, Paintingi>; as well as several other subclasses. Each subclass includes a loosely hierarchical arrangement of the topics pertinent to the subclass, going from the general to the more specific. Individual topics are often broken down by specific places, time periods, or bibliographic forms (such as periodicals, biographies, etc.). Each topic (often referred to as a caption) is assigned a single number or a span of numbers. Whole numbers used in LCC may range from one to four digits in length, and may be further extended by the use of decimal numbers. Some subtopics appear in alphabetical, rather than hierarchical, lists and are represented by decimal numbers that combine a letter of the alphabet with a numeral , e.g. .B72 or .K535. Relationships among topics in LCC are shown not by the numbers that are assigned to them, but by indenting subtopics under the larger topics that they are a part of, much like an outline. In this respect, it is different from more strictly hierarchical classification systems, such as the Dewey Decimal Classificationi>, where hierarchical relationships among topics are shown by numbers that can be continuously subdivided.

The Library of Congress Subject Headings Supplemental Vocabularies: Children’s Headings (LCSHAC) is a thesaurus which is used in conjunction with LCSH. It is not a self-contained vocabulary, but is instead designed to complement LCSH and provide tailored subject access to children and young adults when LCSH does not provide suitable terminology, form, or scope for children. LCSHAC records can be identified by the LCCN prefix "sj".

The Library of Congress Genre/Form Terms for Library and Archival Materials (LCGFT) is a thesaurus that describes what a work is versus what it is about. For instance, the subject heading Horror films, with appropriate subdivisions, would be assigned to a book about horror films. A cataloger assigning headings to the movie The Texas Chainsaw Massacre would also use Horror films, but it would be a genre/form term since the movie is a horror film, not a movie about horror films.

The thesaurus combines both genres and forms. Form is defined as a characteristic of works with a particular format and/or purpose. A "short" is a particular form, for example, as is "animation." Genre refers to categories of works that are characterized by similar plots, themes, settings, situations, and characters. Examples of genres are westerns and thrillers. In the term Horror films "horror" is the genre and "films" is the form.

LCGFT assumed its title in June 2010 and in May 2011 the LCCN prefix "gf" was implemented to identify Genre/form terms as part of the change to separate LCGFT from LCSH. The "gf" prefix is one way by which a record can be identified as a genre/form authority record. Further information about the LCGFT thesaurus and its relationship to the LCSH data set may be found in Library of Congress to Reissue Genre/Form Authority Records (Revised May 9, 2011) and in a FAQ on the topic.