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a compilation of semantic units of a language according to a given system of semantic relationships. A thesaurus actually defines the semantics of a language, whether a national language, the language of a specific science, or a formalized language for use in an automated control system.
Originally, the thesaurus was regarded as a monolingual dictionary in which semantic relationships were defined by groupings of words under thematic headings. For example, the English thesaurus of P. M. Roget published in 1962 (1st ed., 1852) contains 1,040 headings for approximately 240,000 words. The index, or key, to this thesaurus consists of an alphabetic list of words with the headings and subheadings to which each word belongs. Traditional thesauri with descriptions of the semantic systems of individual languages have been published for English, French, and Spanish. Monolingual dictionaries that provide the basic semantic field of each word, such as S. I. Ozhegov’s Russian dictionary, are quite close to thesauri.
In the 1970’s thesauri for information languages became widespread. In such thesauri, special lexical units, known as descriptors, are selected for use in automatic information retrieval. A synonymous descriptor is correlated with each word in the thesaurus, and semantic relations for the descriptions are clearly indicated, such as genus/species, part/whole, and end/means. Generic-specific (hierarchial) relationships are usually separated from associative relationships. Thus, the Information Retrieval Thesaurus for Information Science, published in the USSR in 1973, provides a dictionary entry for each descriptor, under which synonymous key words and generic, specific, and associative descriptors are listed separately. Semantic arrangements of thematic classes have been appended to this thesaurus to facilitate orientation of the associative links between descriptors. In automated information retrieval, the documents searched have indexes that contain the descriptors given in the inquiry and other descriptors having certain semantic relationships to the inquiry descriptors.
It is sometimes useful to distinguish in a thesaurus those concrete associative relationships that are specific for a given thematic field, such as illness/cause, instrument/use, or instrument/ quantity measured. The position of a lexical unit (a word or word combination) in a thesaurus characterizes the unit’s meaning in the language. Knowledge of the system of semantic relationships entered into by a given word, including the heading under which it is entered, makes it possible to judge the meaning of the word.
In the broad sense, a thesaurus is interpreted as a description of the system of knowledge about reality possessed by an individual bearer of information or by a group of bearers. The bearer may also fulfill the functions of a receiver of additional information, as a result of which his thesaurus also changes. In this case the initial thesaurus determines the receiver’s capacity to obtain semantic information. Those characteristics of the thesauri of individuals manifested in the apprehension and understanding of information are investigated in psychology and in the study of systems with artificial intelligence. Those characteristics of the thesauri of individuals and groups that permit mutual comprehension on the basis of commonality of thesauri are studied in sociology and communications theory. In these situations, thesauri must also be made to include the complex expressions and their semantic relationships, constituting the fund of information possessed by complex systems. Thesauri actually contain not only information about reality, but metainformation (information about information), making possible the reception of new information.
REFERENCESChernyi, A. I. “Obshchaia metodika postroeniia tezaurusov.” Nauchno-tekhnicheskaia informatsiia: Ser. 2, 1968, no. 5.
Varga, D. Metodika podgotovki informatsionnykh tezaurusov. Moscow, 1970. (Translated from Hungarian.)
Shreider, Iu. A. “Tezaurusy v informatike i teoreticheskoi semantike.” Nauchno-tekhnicheskaia informatsiia. Ser. 2, 1971, no. 3.
IU. A. SHREIDER