Academic journal article Library Resources & Technical Services

Library of Congress Classification Numbers: Issues of Consistency and Their Implications for Union Catalogs

Academic journal article Library Resources & Technical Services

Library of Congress Classification Numbers: Issues of Consistency and Their Implications for Union Catalogs

Article excerpt

This study examined Library of Congress Classification (LCC)-based class numbers assigned to a representative sample of 200 titles in 52 American library systems to determine the level of consistency within and across those systems. The results showed that under the condition that a library system has a title, the probability of that title having the same LCC-based class number across library systems is greater than 85 percent. An examination of 121 titles displaying variations in class numbers among library systems showed certain titles (for example, multi-foci titles, titles in series, bibliographies, and fiction) lend themselves to alternate class numbers. Others were assigned variant numbers either due to latitude in the schedules or for reasons that cannot be pinpointed. With increasing dependence on copy cataloging, the size of such variations may continue to decrease. As the preferred class number with its alternates represents a title more fully than just the preferred class number, this paper argues for continued use of alternates by library systems

and for finding a method to link alternate class numbers to preferred class numbers for enriched subject access through local and union catalogs.


As long ago as 1968 the possibility of searching for resources in online catalogs through assigned call numbers as access points was raised. (1) A call number is a notation that uniquely identifies an item within a collection and on the shelf. It is a composite number containing a class number that indicates the class that its subject belongs to as per a classification scheme, such as the Library of Congress Classification (LCC) scheme, and a book or an item number that uniquely identifyies an item within that class, derived usually from the author's name and other physical features (e.g., volume number). (2) Today that possibility has been realized; many library catalogs provide call number searches. Some even allow searching by the class number part of the call number. For instance, OCLC's WorldCat, originally a cataloging resource, is becoming increasingly accessible to the public and allows searching and browsing by the class number part of the assigned call number. Moreover, networked resources are often assigned class numbers using the same classification schemes that are being used by the libraries to classify their resources. (3)

A searcher who chooses to search by call or class number can reasonably expect all institutions to have the same class number for a particular title, given that the same classification scheme was used as a source for class numbers, and only one class number was assigned, even for a multi-foci title. In this context, the objective of dais study was to ascertain the degree of uniformity of class number assignment that exists within libraries and across different libraries and, where deviations exist, to analyze the reasons for deviations and their implications for local and online catalog design in general, and in academic library catalogs in particular.


The many advantages of call numbers in general, and class numbers in particular, as access points over author and title access points have been well-documented. (4) Unlike vocabulary searching, call number searching is precise and unambiguous. Unless a cataloger provides for various vocabulary approaches, such as variant spellings and synonyms, a user may miss relevant items. In contrast, call numbers consist of unambiguous sequences of letters, numerals, or both. There are no two ways to represent the same class number. Thus, call numbers are more precise than vocabulary terms as search tools. Moreover, they are becoming more available as search tools as more and more network resources are being classified using general library classification schemes.

More importantly, call numbers serve as starting points for browsing shelves. Arrangement by call numbers on the shelves results in the collocation first by class numbers and then book numbers. …

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