Guidelines for Multilingual Thesauri

by Working Group on Guidelines for Multilingual Thesauri

Series: IFLA Professional Reports 115

Multilingual indexing vocabularies exist in different forms, e.g. subject heading lists, thesauri, enumerative classifications, analytico-synthetic classifications. In a multilingual indexing vocabulary both the terms and the relationships are represented in more than one language.

In this document the emphasis is on multilingual thesauri. Since the drawing up of the Guidelines for the Establishment and Development of Multilingual Thesauri in the 1970s two developments have played important roles in the thinking about multilingual access to information: the building of nonsymmetrical thesauri and the linking of two or more thesauri and/or controlled vocabularies.

There are three approaches in the development of multilingual thesauri:

  1. Building a new thesaurus from the bottom up.
    a. starting with one language and adding another language or languages
    b. starting with more than one language simultaneously
  2. Combining existing thesauri.
    a. merging two or more existing thesauri into one new (multilingual) thesaurus to be used in indexing and retrieval
    b. linking existing thesauri and subject heading lists to each other; using the existing thesauri and/or subject heading lists both in indexing and retrieval
  3. Translating a thesaurus into one or more other languages.

In the last case the languages involved are not treated equally. The language of the existing thesaurus becomes the dominant language1. This approach is not discussed in this document.

Linking is typically used in situations where different agencies are using their own indexing vocabularies in their own languages for their own information systems. The linking makes it possible for the end-user to search in all linked indexing vocabularies using any one of the linked thesauri or subject heading lists. An example of a multilingual linking project is the MACS (Multilingual Access to Subjects) project.

Building from the bottom up is only viable in cases where a new thesaurus or subject heading list is envisaged. The main advantage is that the languages involved can be treated equally.

In both approaches dealt with in this document two groups of problems are encountered:

a) Equivalence problems
Semantic problems pertain to equivalence relations between preferred and non-preferred terms in thesauri or subject heading lists. Equivalence relations exist not only within each separate language involved (intra-language equivalence), but also between the languages (inter-language equivalence).

Intra-language homonymy and inter-language homonymy are also considered semantic issues. Additional problems pertaining to semantics involve the scope, form and choice of thesaurus terms.

b) Structural problems
Structural problems involve hierarchical and associative relations between the terms. An important question in this respect is whether the structure should be the same or different for each language. In most if not all cases of linking, the structure will most probably not be the same in all the indexing vocabularies involved. In other approaches mentioned, it is possible in principle to apply the same structure to all languages. This question will be discussed later.(see § 3.2)

A glossary appears at the end of the document.

Guidelines for Multilingual Thesauri
Compiled by a Working Group on Guidelines for Multilingual Thesauri of IFLA Classification and Indexing Section chaired by: Gerhard J. A. Riesthuis and Patrice Landry The Hague, IFLA Headquarters, 2009. - 30p. 30 cm.
(IFLA Professional Reports : 115)
ISBN 978-90-77897-35-5
ISSN 0168-1931

Original language


Ordering Information

Order directly from IFLA Headquarters (address on order form) for EUR 20 per report, plus 17.00 postage and handling charges and VAT, if applicable.

Order form

Guidelines, Subject Analysis and Access

Last update: 28 October 2016