ISO 25964 is the international standard for thesauri, published in two parts as follows: ISO 25964 Information and documentation - Thesauri and interoperability with other vocabularies Part 1: Thesauri for information retrieval [published August 2011] Part 2: Interoperability with other vocabularies [published March 2013] It was issued by ISO, the International Organization for Standardization, and its official website is maintained by its secretariat in NISO, the USA National Information Standards Organization. Each part of the standard can be purchased separately from ISO or from any of its national member bodies (such as ANSI, BSI, AFNOR, DIN, etc.). Some parts of it are available free of charge from the official website. History The first international standard for thesauri was ISO 2788, Guidelines for the establishment and development of monolingual thesauri, originally published in 1974 and updated in 1986. In 1985 it was joined by the complementary standard ISO 5964, Guidelines for the establishment and development of multilingual thesauri. Over the years ISO 2788 and ISO 5964 were adopted as national standards in several countries, for example Canada, France and UK. In the UK they were given alias numbers BS 5723 and BS 6723 respectively. And it was in the UK around the turn of the century that work began to revise them for the networking needs of the new millennium. This resulted during 2005 - 2008 in publication of the 5-part British Standard BS 8723, as follows: BS 8723 Structured vocabularies for information retrieval - Guide Part 1: Definitions, symbols and abbreviations Part 2: Thesauri Part 3: Vocabularies other than thesauri Part 4: Interoperability between vocabularies Part 5: Exchange formats and protocols for interoperability Even before the last part of BS 8723 was published, work began to adopt and adapt it as an international standard to replace ISO 2788 and ISO 5964. The project was led by a Working Group of ISO's Technical Committee 46 (Information and documentation) Subcommittee 9 (Identification and description) known as “ISO TC46/SC9/WG8 Structured Vocabularies”. ISO 2788 and ISO 5964 were withdrawn in 2011, when they were replaced by the first part of ISO 25964. The second part of ISO 25964 was issued in March 2013, completing the project. Aims and Scope ISO 25964 is for thesauri intended to support information retrieval, and specifically to guide the choice of terms used in indexing, tagging and search queries. The primary objective is thus summarised in the introduction to