A controlled vocabulary is an organized set of terms (words and phrases) meant to facilitate description and retrieval of items in a collection. These terms can be in alphabetical or hierarchical order, and are often developed to describe a certain type of collection, such as the Art & Architecture Thesaurus or the Nomenclature for Museum Cataloging (although that does not mean that they can only be used for that type of collection). Controlled vocabularies can be used to describe the subject of an item, the form or genre of an item, or even provide information about its provenance.
Controlled vocabularies can be organized in several ways. Two of the most common forms are subject heading lists and thesauri.
Subject headings are words used for describing the subject of an item, in order to retrieve groups of items on a particular topic (i.e. books about Shakespeare, or art depicting Romeo and Juliet). Subject heading lists are usually arranged alphabetically rather than thematically or hierarchically; they provide the preferred terms for topics along with cross-references to alternative terms. The Library of Congress Subject Headings are probably the best-known example of this kind of vocabulary.
A thesaurus, in contrast, organizes its terms hierarchically, since its main emphasis is on the relationships between terms. Like a subject heading list, it provides preferred terms and cross-references, but also includes relationship indicators with each term. For instance, the Art & Architecture Thesaurus indicates that Bibliographies are a form of the concept Lists (which are in turn a Document Genre). A thesaurus represents a semantic network, not just a flat list of terms.
Taxonomies, authority files, and classification schemes are all examples of controlled vocabularies as well. If you'd like to read about controlled vocabularies in more detail, the Getty Institute has produced a comprehensive and freely-available Introduction to Controlled Vocabularies.
Controlled vocabularies at the Folger
Folger catalogers use several controlled vocabularies (both subject heading lists and thesauri) to fit the needs of different materials. These controlled vocabularies are used in several ways:
Controlled vocabularies most frequently appear in MARC fields 600, 610, 630, 650, 651, and 655. When they are from any vocabulary other than LCSH, the source vocabulary is indicated in a subfield ‡2 following the term (see the Subject heading term source code list and the Genre/form term source code list for more information). The Folger generally uses non-LCSH terms as genre/form headings only; they can be found in the 655 field.
The Library of Congress Subject Headings thesaurus is a general thesaurus, first developed by the Library of Congress in 1898, and actively maintained and updated since then. At the Folger, it is used to specify subjects for both open stacks and Vault materials.
600 10 Shakespeare, William, 1564-1616 ‡x Homes and haunts ‡v Pictorial works
650 0 Political corruption ‡z England ‡v Early works to 1800
In the two examples above, notice that there is a subfield ‡v present. LCSH is unusual in that it does not include only subject terms, but also genre terms and chronological and geographical divisions. The subfield ‡v indicates a genre/form term: "Pictorial works" indicates that images are a central part of an item, and "Early works to 1800" indicates that the item is a work printed or issued before 1800. Even though the items are not necessarily about pictures or early modern printing, they are examples of those things. Genre subdivisions are gradually being phased out of practice as the Library of Congress develops more specialized vocabularies and library catalogs implement faceted browsing, but for now many are still actively used.
The LCSH is a broad, generalized vocabulary, and it can describe a variety of materials. However, it can be difficult to describe certain items fully using only LCSH, especially in the case of the Folger's specialized early modern collections. To this end, Folger catalogers turn to a selection of smaller but more specialized vocabularies: the RBMS controlled vocabularies, the Art & Architecture Thesaurus, and occasionally the Thesaurus for Graphic Materials (as well as a small handful of local terms).
Like Library of Congress Classification, LCSH was created to fit the Library of Congress's holdings, and not to encompass all areas of knowledge or topics. This is another reason LCSH terms are often not ideal for Folger holdings.
The Rare Book and Manuscripts Section (part of the American Library Association) maintains six controlled vocabularies relating to the physical evidence, providence, and genre of rare materials. RBMS terms are used extensively by the Folger as genre and form terms to describe our Vault collections, and some of our open stacks items as well (such as to note the presence of an author's inscription); they are also used to describe items in the Folger Bindings Image Collection. Terms from the Genre vocabulary are added to records as-is, but terms from the other RBMS vocabularies include the vocabulary name in following parentheses: i.e., "Prayer books" vs. "Prize books (Provenance)." The RBMS vocabularies account for seven abbreviations on the list of source codes for genre & form terms (printing and publishing terms get distinct abbreviations, despite being combined into a single thesaurus).
Composition errors (Printing). ‡2 rbpri
Printed waste (Binding). ‡2 rbbin
Volvelles. ‡2 rbgenr
The Art & Architecture Thesaurus is a true hierarchical thesaurus. By contrast, LCSH is not, though it does include broader and narrower terms. Maintained by the Getty Research Institute, AAT is broader than its name implies. Its coverage of art topics is useful at the Folger, but AAT is also designed to describe topics depicted in art. The Folger commonly uses AAT in authority control. In terms related to the book trade, especially, AAT is more granular and expressive than LCSH.
Index terms for occupations in archival and manuscript collections (ITOAMC) is a controlled vocabulary maintained as an Excel spreadsheet by Manuscript Division of the Library of Congress for use in authority and bibliographic records. It does not seem to be available on the Library of Congress web site, so the listing on Folgerpedia may be the easiest way to access the controlled vocabulary.
ITOAMC, as its name implies, focuses on occupations (e.g., Archivists, Pianists) and other designations for persons (e.g., Civil libertarians, Quakers). At the Folger, it is used almost exclusively in authority control. But like LCSH, ITOAMC has American bias by design. It has terms, like "American loyalists" and "Chaplains, U.S. Senate", that would rarely come up here—and none particular to, say, the English Civil War. Thus, ITOAMC is often a third choice for Folger catalogers, after AAT and LCSH.
The Thesaurus for Graphic Materials was initially created by the Library of Congress to provide subject indexing for pictorial works, and was designed with automated systems, such as machine-readable cataloging in mind. At its creation in 1995, it consisted of two vocabularies: subject terms (TGM I) and genre and physical characteristic terms (TGM II). In October 2007, TGM I and TGM II were merged into a single thesaurus; however, due to their differing uses, they are still designated by two different sources codes in the MARC subfield ‡2. TGM I terms usually appear in the 650 field and are designated by ‡2 lctgm, while TGM II terms appear almost exclusively in the 655 field and are designated by ‡2 gmgpc.
One of TGM's strengths is its emphasis on providing subject access for both the "of" and the "about" of graphic materials - not just the subjects that are directly depicted, but also the broader meanings or symbolism that those subjects may suggest. TGM does not always have the granularity and deep hierarchical structure of AAT; however, it is a living vocabulary, and is regularly updated. It is occasionally used by Folger catalogers for bibliographic records, particularly for items in the Folger Art collections, when a more appropriate term cannot be found in LCSH, RBMS, or AAT.
- Controlled vocabulary on Wikipedia