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An index is a guide, in an electronic or print form, used to locate information in documents, files, publications, or a group of publications. It is often listed in alphabetical or numerical order, arranged by subjects, authors, titles, and types of publications.
The traditional back-of-the-book index is a list of words that point to where those words can be found in a document. The words or phrases are selected by an indexer and the pointers are page numbers, paragraphs, or section numbers.
The Periodical index is a guide used to locate articles in periodicals such as journals, magazines, and newspapers. A Search engine is a web based index.
An index is designed to help the reader find information quickly and easily. A complete and truly useful index is not simply a list of the words and phrases used in a publication (which is properly called a concordance), but it is an organized map of its contents, including cross-references, grouping of like concepts, and other useful intellectual analysis.
Sample back-of-the-book index excerpt:
In books, an index is usually placed near the end (this is commonly known as "BoB" or back-of-book indexing). They complement the table of contents by enabling access to information by specific subject, whereas contents listings enable access through broad divisions of the text arranged in the order they occur.
There are several types of index. Back-of-the-book index indicates pages, sections, chapters, a listed word (subject, name, title) appear or is explained in the book. Sub-entries and cross references are sometimes provided to the listed term.
A periodical index is an index for articles of periodical literature such as journals, magazines, and newspapers.
A citation index is an index of citations between publications, allowing the user to easily establish which later documents cite which earlier documents. The Impact factor, often abbreviated IF, is a measure of the citations to science and social science journals. It is frequently used as a proxy for the importance of a journal to its field.
Subject indexing involves two steps.
To maintain a consistency of indexing, a set of indexing rules and guidelines can be established prior to indexing.
An indexer first analyzes what a document is about. An indexer identifies the range and scope of coverage, perspectives, types of research, disciplinary areas, and other specific information the document provides. The level of indexing specificity and other details of indexing are determined primarily by user group needs. If a user group is a specialist in a certain field, indexer needs to tailor index to their specific needs.
After a conceptual analysis, an indexer translates his or her conceptual analysis to index terms. Conversion of conceptual analysis into index terms is called translation. There are basically two methods of translation: Derivative Indexing and Assignment Indexing. These two methods are distinguished by a difference concerning how and where index terms are obtained.
An indexer finds terms or phrases used in the document and extracts them as index terms. An indexer often extracts words or phrases from the title, abstract, and a table of contents.
For this type of indexing, an indexer selects index terms not from the documents but from controlled vocabularies which are a set of preselected, predefined terms. Those index terms may or may not appear in any part of the document. A collection of controlled vocabularies is called thesaurus in information science.
One of the most important principles of indexing is specificity of index terms. An indexer uses the most specific terms that can cover the topic. Rather than a single broad term, an indexer uses several specific terms that can exhaustively cover the topic.
Another important principle of indexing is to give multiple access points to the information. A retrieval rate of a document increases if it can be found from multiple indexed topics.
The indexing process usually begins with a reading of the text, during which indexable (significant) concepts are identified and the terms to be used to represent those concepts are selected and sometimes marked (e.g. with a highlighter), or more likely, entered into a professional indexing software program. The indexer may make a second pass through the text during which he or she enters the terms into an index document, creating subentries where appropriate. Professional indexing software handles such tasks as formatting the index and arranging the entries into alphabetical order. The final task involves editing to improve consistency, accuracy, and usefulness, and to ensure it follows publisher's guidelines.
Indexers must analyze the text to enable presentation of concepts and ideas in the index that may not be named within the text. The index is meant to help the reader, researcher, or information professional, not the author, find information, so the professional indexer must act as a liaison between the text and the its ultimate user.
Indexing is often done by freelancers hired by publishers or book packagers. Some publishers and database companies employ indexers.
There are indexing software programs available to assist with the special sorting and copying needs involved in index preparation. They include Cindex, Macrex, and SkyIndex.
An increasing interest in the use of electronic documents has led to the development of embedded indexing, where index terms are inserted into appropriate places in one or more source documents using some kind of markup language. An accurate, sorted list of these marked index terms ("index entries") can then be generated dynamically from the source document(s) at any time. This is a standard, yet little known, feature of many popular word processing programs such as Microsoft Word, StarWriter/Openoffice.org Writer, and WordPerfect.
Everyone has experienced a bad index; it's almost worse than no index at all. Some principles of good indexing include:
Some indexers specialize in specific formats such as scholarly books, microforms, web indexing (the application of a back-of-book-style index to a website or intranet), search engine indexing, database indexing (the application of a pre-defined controlled vocabulary such as MeSH to articles for inclusion in a database), periodical indexing (indexing of newspapers, journals, magazines).
Some indexers specialize in particular subject areas, such as anthropology, business, computers, economics, education, government documents, history, law, mathematics, medicine, psychology, and technology.
Kurt Vonnegut's novel Cat's Cradle includes a character who is a professional indexer and believes that "indexing [is] a thing that only the most amateurish author [undertakes] to do for his own book." She claims to be able to read an author's character through the index he created for his own history text, and warns the narrator, an author, "Never index your own book."
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