Controlled vocabulary

Controlled Vocabulary in Library and Information Science
– Controlled vocabulary is a carefully selected list of words and phrases used to tag information units for easier retrieval.
– It solves problems of homographs, synonyms, and polysemes by establishing a clear relationship between concepts and preferred terms.
– Preferred terms are chosen based on user warrant, literary warrant, and structural warrant.
– Controlled vocabularies handle homographs with qualifiers to ensure each term refers to one concept.
– Examples of controlled vocabulary systems include the Library of Congress Subject Headings.

Types of Controlled Vocabulary Tools Used in Libraries
– Subject headings and thesauri are the main kinds of controlled vocabulary tools used in libraries.
– Subject headings describe whole books, while thesauri cover specific disciplines.
– Subject headings tend to have terms in indirect order, while thesaurus terms are always in direct order.
– Subject headings often use pre-coordination of terms, while thesauri use singular direct terms.
– Thesauri list equivalent, narrower, broader, and related terms, while subject headings historically did not.

Indexing Languages
– There are three main types of indexing languages: controlled, natural language, and free indexing.
– Controlled indexing language allows only approved terms for describing documents.
– Natural language indexing language allows the use of any term from the document being described.
– Free indexing language allows the use of any term, even if it’s not from the document.
– Indexers choose the level of indexing exhaustivity, which determines the level of detail in describing the document.

Advantages of Controlled Vocabularies
– Controlled vocabularies improve the accuracy of free text searching by reducing irrelevant items in the retrieval list.
– They eliminate ambiguities caused by the inherent ambiguity of natural language.
– Using controlled vocabulary can significantly increase the precision of an information retrieval system.
– Controlled vocabulary can enhance recall by eliminating the need to search for synonymous terms.
– It improves the performance of information retrieval systems compared to free text searching.

Problems with Controlled Vocabularies
– Controlled vocabulary searches may have unsatisfactory recall, failing to retrieve relevant documents.
– Users must have a deep understanding of the controlled vocabulary to avoid missing relevant documents.
– Low indexing exhaustivity may result in important aspects of a document not being described with index terms.
– Some articles may not be tagged with the correct term if it is considered secondary to the main focus.
– Controlled vocabulary requires expertise and careful selection of terms to address these problems.