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Subject Cataloging

Subject Cataloging (or Subject Cataloguing)

Subject Cataloging (or Subject Cataloguing) involves the subject analysis of the resource and providing corresponding subject headings from a controlled vocabulary or subject heading list, such as Library of Congress Subject Headings (LCSH), Medical Subject Headings (MESH) and assignment of classification numbers using schemes such as Library of Congress Classification (LCC) or Dewey Decimal Classification (DDC).

Subject Heading is defined as the most specific word or group of words that capture the essence of the subject or one of the subjects of a book or other library material which is selected from a subject heading list containing the preferred subject access terms (controlled vocabulary) and assigned as an added entry in the bibliographic record which works as an access point and enables the work to be searched and retrieved by subject from the library catalog database. Classification or Library Classification is the process of arranging, grouping, coding, and organizing books and other library materials on shelves or entries of a catalog, bibliography, and index according to their subject in a systematic, logical, and helpful order by way of assigning them call numbers using a library classification system, so that users can find them as quickly and easily as possible. Use of classification enables library users to browse on shelves to find its materials, determines the place of a book and the shelf, and also collocates additional items on the same or related subjects. Classification also enables the library users to find out what documents the library has on a certain subject. The cataloger assigns a classification, or call number, in correlation with the subject headings.

Janis L. Young and  Daniel N. Joudrey¹ describe Subject Cataloging as below:

Subject cataloging is the phase of the cataloging process which is concerned with determining and describing the intellectual or artistic content and the genre/form characteristics of a resource, and translating that understanding into subject headings and classification notations.

After the resource’s aboutness has been determined, as many subject headings as are appropriate are chosen from a standard list. There are many such lists, including: Library of Congress Subject Headings (known as LCSH), the LC Genre/Form Terms for Library and Archival Materials, Medical Subject Headings (which is often referred to as MeSH), the Art and Architecture Thesaurus, and so on.

In addition, a classification notation is chosen from whatever classification scheme is used by the library. In the United States, the most likely candidates are the Library of Congress Classification (often referred to as LCC) or the Dewey Decimal Classification (known as DDC).

Traditionally in the U.S., the classification serves as a means for bringing a resource into close proximity with other resources on the same or related subjects. In the case of tangible resources, the classification is the first element of the call number, which is a device used to identify and locate a particular resource on the shelves. 

Subject Cataloging Phases
  • Two Phases of Subject Cataloging
    • Conceptual analysis
      • What is it about?
      • What is its form or genre?
    • Translation
      • Controlled vocabulary terms
      • Classification

Two popular methods of Subject Cataloging are: (1) Controlled vocabulary terms, and (2) Classification schemes. One popular controlled vocabulary terms list is the Library of Congress Subject Headings (LCSH) and one popular library classification scheme is the Library of Congress Classification. These are described in brief below:

Library of Congress Subject Headings (LCSH) - Library of Congress Subject Headings (LCSH) is the list of headings produced from the subject authority file maintained by the United States Library of Congress for use in bibliographic records. It is popularly known by its abbreviation as LCSH and is sometimes used interchangeably with the phrase subject authority file. LCSH is a multidisciplinary vocabulary that includes headings in all subjects, from science to religion, to history, social science, education, literature, and philosophy. It also includes headings for geographic features, ethnic groups, historical events, building names, etc. Library of Congress Subject Headings (LCSH) is the most widely used subject vocabulary in the world. It is the model for many other vocabularies in English and other languages and has been translated into numerous languages. The strongest aspect of LCSH is that it represents subject headings of the Library of Congress, the national library of the United States, one of the richest of national libraries of the world. The administrative and managerial machinery of LC has made it possible for LCSH to stand out as an undisputed leader. LCSH is also used as indexing vocabulary in a number of published bibliographies. LCSH comprise a thesaurus or a controlled vocabulary of subject headings which is used by a cataloger or an indexer to assign subject headings to a bibliographic record to represent the subject of a work he/she is cataloging. LCSH contain the preferred subject access terms (controlled vocabulary) that are assigned as an added entry in the bibliographic record which works as an access point and enables the work to be searched and retrieved by subject from the library catalog database. The controlled vocabulary identifies synonym terms and selects one preferred term among them to be used as the subject heading. For homonyms, it explicitly identifies the multiple concepts expressed by that word or phrase. Cross-references are used with headings to direct the user from terms not used as headings to the term that is used, and from broader and related topics to the one chosen to represent a given subject. The fortieth edition of Library of Congress Subject Headings (LCSH 40) contains headings established by the Library through January 2018. The headings included in this list were obtained by creating a file consisting of all subject heading and subdivision records in verified status in the subject authority file at the Library of Congress. There were 342,947 authority records in the file then. The subject authority database from which the headings in this edition were drawn indicates that the file contains approximately 24,390 personal name headings of which 23,272 represent family names, 10,034 corporate headings, 6 meeting or conference headings, 481 uniform titles, 242,511 topical subject headings, and 61,885 geographic subject headings. There are 764 general USE references, 4,351 general see also references, 299,751 references from one usable heading to another, and 362,646 references from unused terms to used headings. The creation and revision of subject headings is a continuous process. Approximately 5,000 new headings, including headings with subdivisions, are added to LCSH each year. Proposals for new headings and revisions to existing ones are submitted by catalogers at the Library of Congress and by participants in the Subject Authority Cooperative Program (SACO). More information on SACO may be found at <URL>. Approved proposals become part of the online authority file of subject headings at the Library of Congress, from which various publications are created. Five services provide information about new and revised headings. First, a distribution service supplies the subject headings in the MARC 21 authorities format via Internet FTP on a weekly basis to supplement the master database file of subject authority records. Second, L.C. Subject Headings Monthly Lists are a timely source of information about new and changed subject headings, class numbers, references and scope notes. The lists are posted monthly to the World Wide Web at Third, Classification Web provides World Wide Web access to Library of Congress Subject Headings and Library of Congress Classification to subscribers. Fourth, subject authority records are included in the Library’s Web authorities service and may be searched and viewed at Fifth, subject authorities are freely available for searching and download through the Library’s Linked Data Service at

Library of Congress Classification - The Library of Congress Classification (LCC) is a system of library classification developed by the Library of Congress. It was 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 Library's Policy and Standards Division maintains and develops the system. In recent decades, as the Library of Congress made its records available electronically through its online catalog, more libraries have adopted LCC for both subject cataloging as well as shelflisting. There are several classification schemes in use worldwide. Besides LCC, the other popular ones among them are Dewey Decimal Classification (DDC), Universal Decimal Classification (UDC), and Bliss Bibliographic Classification (BC). Out of these, DDC and LCC are the classification systems which are most commonly used in libraries. The potential of Library of Congress Classification (LCC) system is yet to be explored in libraries. This article describes the various aspects of LCC and its suitability as a library classification system for classifying library resources. The Library of Congress was established in 1800 when the American legislatures were preparing to move from Philadelphia to the new capital city of Washington, D.C. Its earliest classification system was by size and, within each size group, by accession number. First recorded change in the arrangement of the collection appeared in the library’s third catalog, issued in 1808, which showed added categories for special bibliographic forms such as legal documents and executive papers. On the night of August 24, 1814, during the war of 1812, British soldiers set fire to the Capitol, and most of the Library of Congress’s collections were destroyed. Sometimes after, Thomas Jefferson offered to sell to Congress his personal library; subsequently, in 1815, the Congress purchased Jefferson’s personal library of 6,487 books. The books arrived already classified by Jefferson’s own system. The library adopted this system and used it with some modifications until the end of the nineteenth century. Library of Congress moved to a new building in 1897. By this time, the Library’s collection had grown to one and a half million volumes and it was decided that Jefferson’s classification system was no longer adequate for the collection. A more detailed classification scheme was required for such a huge and rapidly growing collection of documents. The Dewey Decimal Classification (DDC), Cutter’s Expansive Classification and the German Halle Schema were studied, but none was considered suitable. It was decided to construct a new system to be called the Library of Congress Classification (LCC). James C.M. Hanson, Head of the Catalog Division, and Charles Martel, Chief Classifier, were made responsible for developing the new scheme. Hanson and Martel concluded that the new classification should be based on Cutter’s Expansive Classification⁴ as a guide for the order of classes, but with a considerably modified notation. Work on the new classification began in 1901. The first outline of the Library of Congress Classification was published in 1904 by Charles Martel and J.C.M. Hanson – the two fathers of Library of Congress Classification. Class Z (Bibliography and Library Science) was chosen to be the first schedule to be developed. The next schedules, E-F (American history and geography), were developed. But E-F were the first schedules to be published, in 1901, followed by Z in 1902. Other schedules were progressively developed. Each schedule of LCC contains an entire class, a subclass, or a group of subclasses. The separate schedules were published in print volumes, as they were completed. All schedules were published by 1948, except the Class K (Law). The first Law schedule—the Law of United States, was published in 1969, and the last of the Law schedules to publish was KB—Religious law, which appeared in 2004. From the beginning, individual schedules of LCC have been developed and maintained by subject experts. Such experts continue to be responsible for additions and changes in LCC. The separate development of individual schedules meant that, unlike other classification systems, LCC was not the product of one mastermind; indeed, LCC has been called “a coordinated series of special classes”. Until the early 1990s, LCC schedules existed mainly as a print product. The conversion of LCC to machine-readable form began in 1993 and was completed in 1996. The conversion to electronic form was done using USMARC (now called MARC21) Classification Format. This was a very important development for LCC, as it enabled LCC to be consulted online and much more efficient production of the print schedules. In the year 2013, the Library of Congress announced a transition to online-only publication of its cataloging documentation, including the Library of Congress Classification. It was decided, the Library’s Cataloging Distribution Service (CDS) will no longer print new editions of its subject headings, classification schedules, and other cataloging publications. The Library decided to provide free downloadable PDF versions of LCC schedules. For users desiring enhanced functionality, the Library’s two web-based subscription services, Cataloger’s Desktop and Classification Web will continue as products from CDS. Classification Web is a web-based tool for LCC and LCSH. It supports searching and browsing of the LCC schedules and provides links to the respective tables to build the class numbers for library resources. LC has also developed training materials on the principles and practices of LCC and made those available for free on its website.

  • Subject Cataloguing



1. Janis L. Young and Daniel N. Joudrey, Library of Congress, "Library of Congress Subject Headings: Online Training," (accessed March 17, 2020).

  • Last Updated: 2020-03-22
  • Written: 2016-05-26

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