Information Retrieval Language

a sign system designed for the description (by means of indexing) of the basic semantic content of texts (documents) or parts of them, as well as for the expression of the semantic content of information requests with the aim of implementing information retrieval. Any abstract information retrieval language consists of an alphabet (a list of elementary symbols), rules of formation, and rules of interpretation. The formation rules establish which combinations of elementary symbols are allowed in the construction of words and expressions, while the interpretation rules establish how these words and expressions are to be understood.

An information retrieval language must establish the lexical-grammatical means required to express the basic semantic content of any text and the meaning of any information request in a given field or subject; it must be unambiguous (permit only one interpretation of each symbol) and convenient for algorithmic comparison and identification (total or partial) of the transcriptions of the basic semantic content of texts and of information requests. In the development of a specific information retrieval language, one takes into account the specific features of the field or subject for which the language is being created, the characteristics of the texts forming the body to be retrieved, and the nature of the information requirements for whose satisfaction the given information retrieval system is being created.

In most information retrieval languages a basic vocabulary (lexicon) is assigned by enumeration and is a fragment of the vocabulary of some natural language. The words selected from the natural language and the word combinations, which together form the basic vocabulary, serve as if they were the alphabet of the given information retrieval language. The formation rules in such an information retrieval language perform a syntactical function. In certain information retrieval languages the basic vocabulary is given (either totally or partially) by a generation method, whereby the formation rules specify how to construct the words out of a given alphabet and how to construct expressions (phrases) out of these words, as well as to specify which of them are well formed. An information retrieval language is distinct from an information language and from machine language. Since the mid-20th century library and bibliographic classifications and descriptor languages have been widely used as information retrieval languages.