In information retrieval, an index term (also known as subject term, subject heading, descriptor, or keyword) is a term that captures the essence of the topic of a document. Index terms make up a controlled vocabulary for use in bibliographic records. They are an integral part of bibliographic control, which is the function by which libraries collect, organize and disseminate documents. They are used as keywords to retrieve documents in an information system, for instance, a catalog or a search engine. A popular form of keywords on the web are tags, which are directly visible and can be assigned by non-experts. Index terms can consist of a word, phrase, or alphanumerical term. They are created by analyzing the document either manually with subject indexing or automatically with automatic indexing or more sophisticated methods of keyword extraction. Index terms can either come from a controlled vocabulary or be freely assigned.
Keywords are stored in a search index. Common words like articles (a, an, the) and conjunctions (and, or, but) are not treated as keywords because it's inefficient. Almost every English-language site on the Internet has the article "the", and so it makes no sense to search for it. The most popular search engine, Google removed stop words such as "the" and "a" from its indexes for several years, but then re-introduced them, making certain types of precise search possible again.
The term "descriptor" was by Calvin Mooers in 1948. It is in particular used about a preferred term from a thesaurus.
The Simple Knowledge Organization System language (SKOS) provides a way to express index terms with Resource Description Framework for use in the context of the Semantic Web.
In web search engines
Most web search engines are designed to search for words anywhere in a document—the title, the body, and so on. This being the case, a keyword can be any term that exists within the document. However, priority is given to words that occur in the title, words that recur numerous times, and words that are explicitly assigned as keywords within the coding. Index terms can be further refined using Boolean operators such as "AND, OR, NOT." "AND" is normally unnecessary as most search engines infer it. "OR" will search for results with one search term or another or both. "NOT" eliminates a word or phrase from the search, getting rid of any results that include it. Multiple words can also be enclosed in quotation marks to turn the individual index terms into a specific index phrase. These modifiers and methods all help to refine search terms, to better maximize the accuracy of search results.
Author keywords
Author keywords are an integral part of literature. Many journals and databases provide access to index terms made by authors of the respective articles. How qualified the provider is decides the quality of both indexer-provided index terms and author-provided index terms. The quality of these two types of index terms is of research interest, particularly in relation to information retrieval. In general, an author will have difficulty providing indexing terms that characterize his or her document relative to other documents in the database.
Examples
- Canadian Subject Headings (CS)
- Library of Congress Subject Headings (LCSH)
- Medical Subject Headings (MeSH)
- Polythematic Structured Subject Heading System (PSH)
- Subject Headings Authority File (SWD)
See also
- Index (publishing)
- Keyword density
- Subject (documents)
- Tag (metadata)
- Tag cloud
References
- Svenonius, Elaine (2009). The intellectual foundation of information organization (1st MIT Press pbk. ed.). Cambridge, Massachusetts: MIT Press. ISBN 9780262512619.
- Cutts, Matt. (2010, March 4). How search works. Retrieved from https://www.youtube.com/watch?v=BNHR6IQJGZs
- CLIO. Keyword search. Columbia University Libraries. Retrieved from http://www.columbia.edu/cu/lweb/help/clio/keyword.html
Further reading
- Ferris, Anna M. (2018). "Birth of a Subject Heading". Library Resources & Technical Services. 62 (1): 16–27. doi:10.5860/lrts.62n1.16.
In information retrieval an index term also known as subject term subject heading descriptor or keyword is a term that captures the essence of the topic of a document Index terms make up a controlled vocabulary for use in bibliographic records They are an integral part of bibliographic control which is the function by which libraries collect organize and disseminate documents They are used as keywords to retrieve documents in an information system for instance a catalog or a search engine A popular form of keywords on the web are tags which are directly visible and can be assigned by non experts Index terms can consist of a word phrase or alphanumerical term They are created by analyzing the document either manually with subject indexing or automatically with automatic indexing or more sophisticated methods of keyword extraction Index terms can either come from a controlled vocabulary or be freely assigned Keywords are stored in a search index Common words like articles a an the and conjunctions and or but are not treated as keywords because it s inefficient Almost every English language site on the Internet has the article the and so it makes no sense to search for it The most popular search engine Google removed stop words such as the and a from its indexes for several years but then re introduced them making certain types of precise search possible again The term descriptor was by Calvin Mooers in 1948 It is in particular used about a preferred term from a thesaurus The Simple Knowledge Organization System language SKOS provides a way to express index terms with Resource Description Framework for use in the context of the Semantic Web In web search enginesMost web search engines are designed to search for words anywhere in a document the title the body and so on This being the case a keyword can be any term that exists within the document However priority is given to words that occur in the title words that recur numerous times and words that are explicitly assigned as keywords within the coding Index terms can be further refined using Boolean operators such as AND OR NOT AND is normally unnecessary as most search engines infer it OR will search for results with one search term or another or both NOT eliminates a word or phrase from the search getting rid of any results that include it Multiple words can also be enclosed in quotation marks to turn the individual index terms into a specific index phrase These modifiers and methods all help to refine search terms to better maximize the accuracy of search results Author keywordsAuthor keywords are an integral part of literature Many journals and databases provide access to index terms made by authors of the respective articles How qualified the provider is decides the quality of both indexer provided index terms and author provided index terms The quality of these two types of index terms is of research interest particularly in relation to information retrieval In general an author will have difficulty providing indexing terms that characterize his or her document relative to other documents in the database ExamplesCanadian Subject Headings CS Library of Congress Subject Headings LCSH Medical Subject Headings MeSH Polythematic Structured Subject Heading System PSH Subject Headings Authority File SWD See alsoIndex publishing Keyword density Subject documents Tag metadata Tag cloudReferencesSvenonius Elaine 2009 The intellectual foundation of information organization 1st MIT Press pbk ed Cambridge Massachusetts MIT Press ISBN 9780262512619 Cutts Matt 2010 March 4 How search works Retrieved from https www youtube com watch v BNHR6IQJGZs CLIO Keyword search Columbia University Libraries Retrieved from http www columbia edu cu lweb help clio keyword htmlFurther readingFerris Anna M 2018 Birth of a Subject Heading Library Resources amp Technical Services 62 1 16 27 doi 10 5860 lrts 62n1 16
