THE INDEXING PROCESS
Subject indexing is a crucial operation in the creation and maintenance of index files as retrieval of information depends to a large extent on the quality of indexing. Useful information may not be retrieved in many cases because this was not identified and represented at the indexing stage. Alternatively, much irrelevant information may be retrieved if indexing is not precise enough. The process of subject indexing involves basically three steps :
The first step towards a successful index is familiarization. The indexer must become conversant with the subject content of the document. The most reliable and certain way to determine the subject content is to read or examine the work in detail. Since this is not always a fair indication of content, it is always wise to look beyond the title for ascertaining the subject content of the document. There are other features of the document also which often provide information relating to the content. These include abstracts, if any, table of contents, chapter headings, preface, introduction, opening phrases of chapters and paragraphs, illustrations, tables, diagrams and their captions, indexes, book jackets, or other accompanying materials. When these elements fail to provide a clear picture of what the document is about, external sources, such as bibliographies, catalogues, and other reference sources may prove helpful. Occasionally, subject specialists may have to be consulted, particularly when the subject matter is unfamiliar to the indexer.
Subject analysis is a second step prior to the selection of index-terms. After examining the document, the indexer needs to follow a logical approach in selecting those concepts which best express its content. The subject content of a document comprises a number of concepts or ideas. The choice of concepts can be related to a scheme of categories recognised as important in the field covered by the document, e.g. phenomena, processes, properties, operations, equipment, etc. Sometimes guidelines are provided that may go some way towards instructing indexers in consistent identification of concepts. For example, in consistent identification of concepts, indexers of "Chemical Abstracts" are instructed to index "every measurement, observation, method, apparatus, suggestion and theory that is presented as new and value in itself; all new chemical compounds and all elements, compounds and other substances for which new data are given".
This instruction establishes the fact that the identification of concepts is related to the subjects undergoing indexing. While selecting the concepts, the indexer does not necessarily need to retain all the concepts identified during the examination of the document. The selection or rejection of concepts depends on the purpose, which can be identified ranging from the production of alphabetical subject indexes to the computerised storage of indexing data elements for subsequent retrieval by computer or other means.
Once the subject analysis of the document is completed, the final step is to represent the selected concepts in the language of indexing system (as index entries). The indexer should be familiar with the indexing tools, and their working rules and procedures in order to ensure that concepts are organised in a usable and "accessible form. The first two steps are same in all subject indexing techniques. The third or final step varies according to whether the representation is through subject headings list or thesaurus. In practice, the indexer will frequently encounter concepts which are not present in the existing list of subject headings or thesaurus. Depending on the system, in use, these concepts may be entered into the system immediately, or the indexer may have to use more generic index terms and the new concepts being proposed as candidates for later edition inclusion.