Library (institution)

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Other Classification Systems

Although the Dewey Decimal, Library of Congress, and Universal Decimal classification systems are used worldwide, librarians have developed alternative classification systems that are used in various countries around the world. For example, in 1933 Indian librarian Shiyali Ramamrita Ranganathan introduced the Colon Classification system, which classifies all knowledge into broad, fundamental concepts. The Colon system then divides these concepts into several distinguishing characteristics, which Ranganathan called facets. The classification system uses colons (:) to distinguish between the various facets in a single notation. The name of the Colon Classification system is derived from its use of the colon in its notation scheme. Although use of the Colon Classification system is limited to a few Indian libraries, Ranganathan’s concept of facet analysis in classifying knowledge has been widely influential. Some of its key concepts have been adopted by subsequent editions of the Dewey and Universal systems, among others.

Libraries that serve users in very specialized fields of knowledge may also develop their own classification systems. They are especially likely to do so if the major library classifications do not adequately provide for the organization of the literature they collect. For example, organizations specializing in the study of mathematics developed the Mathematics Subject Classification to categorize material on advanced mathematical theory covered in specialized academic journals. The Mathematics Subject Classification allows mathematicians to classify works to a much greater degree of specificity than any of the major systems would allow.

Numerous classification systems have been created for use in other special libraries as well. The National Library of Medicine classification system, for example, has been adopted by most major medical libraries in the United States. That system, which is structured like the Library of Congress Classification, uses the letter W (unused by the Library of Congress system) for medical works. It also takes advantage of unused parts of the Library of Congress Classification class Q, for science. For other subject areas, the National Library of Medicine system applies the Library of Congress Classification unchanged.

C

Subject Headings

Many single works in a library deal with multiple subjects. These works may be difficult to classify using traditional classification systems such as Dewey Decimal Classification or Library of Congress Classification, because these systems typically assign only one classification number to each item. As a result, only one subject is represented, and the work’s other topics are not expressed in the classification number. Users searching the library’s catalog under one of the alternate topics would never find that particular work. To avoid this problem, most libraries also identify their materials with subject headings, which assign multiple index terms to a work. This enables users to find works using any of a number of different search terms. Subject headings may be single words, compound words, or phrases that describe the subjects of a given document. Subject headings are particularly useful for executing online searches, which allow for a high degree of flexibility in identifying search terms.

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In the United States, the two most frequently used systems for creating subject headings are those developed by the Library of Congress (LC) and the Sears List. The LC subject headings, first introduced in 1914, provide detailed terms for a vast number of topics. The LC headings are used in academic libraries, medium-sized to large public libraries, and many special libraries. The Sears List, developed in 1923 by American librarian Minnie Earl Sears, consists of a much smaller set of terms and is designed primarily for public and school libraries. The two lists are not entirely compatible and cannot be used in the same catalog.

Unlike index entries in an individual book, subject headings are generally used only if a major portion of the work deals with that particular subject. Under Library of Congress guidelines, at least 20 percent of a document must address a given subject for a subheading on that subject to be assigned to the book. Examples of LC subject headings include:

• Rivers
• Functional literacy
• Group homes for children
• Education, Preschool
• Burnout (Psychology)

All of the works in a library’s collection that deal with rivers in general would be listed in the catalog under the “Rivers” subject heading. Works dealing with a specific river, such the Mississippi River, would be indexed under the name of that river. “Rivers” is a relatively straightforward subject; subject headings may also represent complex concepts for works dealing with more than one theme. In order to express complex subjects, catalogers add subdivisions to the basic headings. These subdivisions can indicate, for example, specific time frames (20th century, 1860s, Middle Ages), geographical areas (Cairo, Pennsylvania, Canada), or the form of the document (bibliography, dictionary, fiction). Subdivisions may be added to the basic heading or combined with other subdivisions. They are usually separated from the subject heading by dashes. For example, the book National Dreams: Myth, Memory, and Canadian History (1997), by Daniel Francis, is listed under the following LC subject headings. Users could find the book by searching under any one of these headings:

• Group identity—Canada
• Popular culture—Canada
• Canada—History

Online computer catalogs provide far greater power for subject searching than do book or card catalogs. Most online catalogs allow users to execute keyword searches by using one or more of the important words in the subject-heading string. In keyword searching, library users can locate the subject heading “Universities and colleges—Graduate work—Examinations” simply by entering the words universities and examinations. This will retrieve catalog entries for all the library’s works on that subject. The keyword approach results in larger, less-targeted retrievals, often requiring the catalog user to review many records to find the works desired. The great advantage of keyword searching is that catalog users do not have to be familiar with the exact wording of the subject heading to locate desired items. In addition, they can easily browse large numbers of related works without having to physically locate the items on the shelves.

D

Locating Library Materials

Visitors to a library can locate materials in different ways, depending on their own particular needs and interests. Someone looking for recreational reading material may wish to simply browse through the library’s selection of recently published best-sellers. Libraries typically maintain a section that showcases these popular materials. Most users, however, come to the library in search of information about a particular subject. The reference desk is often the best place for these users to start their search, because reference librarians are trained to help library users locate the materials they need. However, users must also learn how to search for information themselves if they are to make the best use of the resources the library has to offer.

Searching for and locating relevant information requires careful thought and strategy. Users can often find answers to their questions by first looking through general reference sources, such as encyclopedias, dictionaries, atlases, and other materials that are usually located near the library’s reference desk. These sources can provide overviews of the subject that may lead to more-detailed sources of information. Users looking for a wide range of literature on a particular subject can search through the library’s catalog, which provides an index of the library’s collection. In addition, users can search through various other indexes, abstracts, and databases. These sources provide references to relevant magazine and journal articles. The Internet can also be a useful source of information.

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Searching the Catalog

Library users can generally find the information they need by searching the library’s catalog, which is an index to all the materials in the library’s collection. Catalog entries typically list each item’s author, its title, its subjects, the date it was published, the name of its publisher, and for some materials, the names of editors, illustrators, or translators. Users can search for items in most online catalogs by entering keywords in any of these categories. Users of specialized collections might have the option of searching for other characteristics of library materials as well. A rare-book collection, for example, might allow users to search for materials by the name of the printer or binder of the book.

By searching through the catalog, users can easily determine whether the library owns works by a particular author or whether it has a work with a specific title. For example, consider a user searching for the book What Is Natural: Coral Reef Crisis (1999), by Jan Sapp. This user could simply conduct a title search of the catalog by typing in What Is Natural: Coral Reef Crisis. Or, by searching under the last name of the author, Sapp, the user could see whether the library has this book or other works by that author.

Searching for materials on a particular subject can be more difficult than searching for materials by authors or title. Before beginning a subject search, the user should first carefully consider various aspects of the information needed, identifying keywords and significant concepts associated with the given subject. These words and concepts can function as possible search terms. If searching under one term turns up too many possible works to realistically examine, a more specific term might be more useful. Likewise, if a search term reveals too few items, the user might achieve more productive results by searching under a more general term.

Some libraries feature union catalogs, which list the holdings of multiple libraries. Users can search union catalogs for materials that are unavailable at their local library but that may be accessible through interlibrary loan. For more information on library catalogs, see the subsection Catalogs in the Organization of Resources section of this article.

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Searching Indexes, Abstracts, and Databases

Even though library catalogs contain listings for every item in a given library’s collection, catalogs do not list individual articles in the library’s magazines and scholarly journals. To find details of articles on a given subject, library users must consult indexes, abstracts, or databases. These resources provide information on articles contained in periodicals, which are publications such as newspapers, magazines, and journals that are issued at regular intervals. Each index, abstract, or database typically focuses on a particular subject or range of related subjects. For example, some indexes list information about articles on art, whereas others contain information about articles on medical issues.

An index of periodicals lists citations containing bibliographic information about each article, including article title, author, publication title, and date of publication. An abstract contains the same information that a periodical index contains, as well as a paragraph or even a few paragraphs summarizing the article. Library databases are indexes and abstracts organized for easy access on a computer. Library databases are typically stored on CD-ROM or accessed via the Internet. Nearly all libraries have printed abstracts and indexes of periodical literature, but periodical information at most libraries is more complete on computer databases.

The Reader’s Guide to Periodical Literature is the best-known print index to English-language periodicals of general interest. Published twice per month, the Reader’s Guide lists articles in more than 150 magazines commonly subscribed to by public and school libraries. It arranges its listings alphabetically by author and subject, but not by title. The Reader’s Guide generally lists six pieces of information in each citation: article title, author, publication title, volume number, page number(s), and date of publication. The Reader’s Guide is cumulated regularly. This means that listings in the latest issues are merged with the previous issue, so that to find recent articles, users need to consult only two or three issues of the Reader’s Guide. Each of the older, bound volumes of the Reader’s Guide covers a two-year period. Some smaller libraries subscribe only to the Abridged Reader’s Guide, which indexes about 45 magazines. The Reader’s Guide series contains listings as far back as 1890. An earlier index, Poole’s Index, provides reference information for English-language articles published from 1802 to 1890. Although the Reader’s Guide is still available in public and school libraries, most library patrons now use computer databases to find magazine and journal articles.

Computer databases typically cover a particular subject or range of subjects. For example, the PsychLIT database contains bibliographic information on articles in the field of psychology. The Modern Language Association Bibliography contains citations for articles in the arts and humanities. The Educational Resources Information Center (ERIC) maintains a database of articles from education journals. Most databases offer only indexed or abstracted information, but some databases, known as full-text databases, provide the entire text of articles. Searching strategies can vary considerably from one database to the next, but most databases give tips to guide users in searching the particular database. In addition, reference librarians are specially trained to assist users in searching through databases.

Many public, academic, and school libraries have compendiums of computer databases, such as the InfoTrac catalogs of databases. Introduced in 1985, InfoTrac catalogs integrate many different kinds of databases into a single collection that can be accessed on CD-ROM or via the Internet. For example, patrons of public or academic libraries can use a single InfoTrac catalog to search computer databases of general interest magazines, government publications, academic journals, legal publications, and health-related periodicals. InfoTrac catalogs in school libraries may be tailored to support classroom assignments at various grade levels. These catalogs typically include computer databases containing the full text of articles in leading magazines, newspapers, and reference books.