List of Subject Headings - General Principles
The rules for subject headings in a dictionary catalogue were formulated by Charles Ammi Cutter in 1876 in his 'Rules for a Dictionary Catalog'. These rules formed the basis of subject headings in American libraries for years to come and are a strong force even today. In respect of subject cataloguing, Cutter stated two objectives:
a) to enable a person to find a book of which the subject is known, and
b) to show what the library has on ' a given subject.
The first objective refers to the need to locate individual items, and the second refers to the need to collocate materials on the same subject. It was on the basis of these needs that Cutter set forth his basic principles of subject entry. They are important because the impact of his principles on construction and maintenance of subject headings is still discernible today. Both, the LCSH and the SLSH adopted the Cutter's principles in assigning subject headings for a document. These are discussed in Unit 16 of this Block. The general principles that guide the indexers in the choice and rendering of subject headings from the standard lisps of subject headings are discussed in the 'following sub-sections.
Specific and Direct Entry
The principles of specific and direct entry require that a document be assigned directly under most specific subject heading that accurately and precisely represents its subject content. If a document is about penguins, it should be entered directly under the most specific heading, that is 'Penguins', it should not be entered under the heading 'Birds' or even under 'Water Birds'. If the name of a specific subject is not available in the list of subject headings, a broader or more general heading may be used. In such cases, the broader heading is the most specific authorized heading in the hierarchy that covers the content of the work. In many cases, several headings may be assigned in order to cover different aspects of a subject.
Common Usage
This principle states that the word(s) used to express a subject must represent common usage. This means that current American spelling and terminology 'Labor', 'Elevators' not 'Lifts' are to, be used. In British libraries these choices would be reversed. According to popular principle, subject headings are to be chosen keeping in mind the needs of the users who are likely to use the catalogue. The popular or common name may be best suited to the readers of a small public library, but in a research or special library, scientific or technical name as heading might be more appropriate: After deciding on the name of heading, the cataloguer should make a reference from the unused heading to the, form used. Such references will be discussed latter under Cross References.
Uniformity
The principle of uniform heading is adopted in order to show what the library collection has on a given subject. One uniform term must be selected from several synonyms, and this term must be applied consistently to all documents on the topic. The heading chosen must also be unambiguous and familiar to all users of the catalogue. Similarly, if there are variant spellings of the same term (e.g. pediatric/paediatric) or different possible forms of the same heading (e.g. air pollution/ pollution/pollution of air), only one is used as the heading. If several meanings are attached to one term, that term must be qualified so that it will be clear to the users for which the meaning is intended. As for example, Crane (Bird)/Crane (Lifting equipment).
Consistent and Current Terminology
It follows from what has been said regarding the justifications for uniform headings that the terminology in headings should be both consistent and current. Two problems are particularly important here: choice among synonyms and change in usage. By principle, common usage prevails when there is a problem of choices among synonymous terms. Standard lists of subject headings designed for general collections prefer a popular term rather than scientific one. In such a situation, a research or special library having specialized library collection and clientele can make extensive modifications of standard lists. Changes in usage also present many practical difficulties. A term chosen on the basis of common usage may become obsolete with the passage of time. Subsequently, a list of subject headings may incorporate current terminology as long as entries pose a problem because of the large number of entries listed under the existing subject headings. In such a situation a subject authority file is to be maintained. Once a heading is changed, every record that was linked to the old heading can be linked to the new heading and this decision is recorded in the subject authority file.
Form Heading
In addition to the subject headings, there are form headings that have the same appearance as topical subject headings but refer to the literary or artistic form (e.g., Essays, Poetry, Fiction, etc.). Libraries that want to provide access to these kinds of materials may assign appropriate form headings to individual works as well as to, collections and materials about the form. Apart from literary works themselves there are also many kinds of library materials about literary forms that require subject headings. For a document on how to write an essay, the heading "Essay" represents a subject and subject headings and form headings can be made by using the singular form for the topical subject heading and plural for the form heading (e.g., Short story, Short stories). In addition to the literary form headings, there are some other form headings that are determined by the general format and purpose of the documents, such as Almanacs, Encyclopaedias, Dictionaries, and Gazetteers.
Cross Reference
Cross-references 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. Three types of cross-references are used in the subject headings structure.
These are discussed below:
See (or USE) references
These references guide users from terms that are not used as headings to the authorized headings for the subject in question. 'See' or 'USE' references ensure that inspite of different names for (or different forms of the name of) a given subject a user shall still be able to locate materials on it.
See also (including BT, NT, and RT) references
These references guide users to the headings that are related either hierarchically or associatively and are used as entries in the catalogue. By connecting related headings, the 'see also' (RT, for related term) references draw the user's attention to material related to his interest. By linking hierarchically related headings, 'see also' (BT, for broader term; NT, for narrower term) references llp, the user to search specific deviations or aspects of his subject of interest.
General references
General references direct the user to a group or category of headings instead of individual headings. It is sometimes called a 'blanket reference'. The provision of general references in the standard list of subject headings obviate the need to make long lists of specific references and thus ensure economy of space.