Friday, March 16, 2012

Taxonomy Standards

I’ve written book reviews before, but recently a journal asked me to review a standard. It was ISO 25964-1 Thesauri and interoperability with other vocabularies, Part 1: Thesauri for information retrieval, which was published in 2011 by the International Organization for Standards. I was pleased to have the opportunity, because this way I obtained a copy which otherwise costs about US$260 (or whatever the current exchange rate equivalence of 238 Swiss Franc). Most taxonomists in the United States and beyond have some familiarity with the U.S. standard ANSI/NISO Z39.19 Guidelines for the Construction, Format, and Management of Monolingual Controlled Vocabularies, not merely because it is American, but because the PDF document is freely available from the National Information Standards Organization (NISO).

So, how do the two standards compare? They are very similar is style, format, level of detail, use of illustrative examples, suitability of a reference, etc. Although explanations are not identical, it is clear that there was some degree of cooperation, consultation, or at least communication among the author teams of each.  The differences between the two standards are in their scope, and that is obvious from their titles. The ISO standard covers both monolingual and multilingual thesauri in a single standard, whereas the ANSI/NISO standard takes up multilingual vocabularies in a separate document. Additionally, the ISO standard focuses on thesauri, leaving other types of vocabularies in the yet-to-be published part 2 document, whereas the ANSI/NISO standard covers all kinds of controlled vocabularies within a single standard publication.

There are implications with these differences. By combining guidance on multilingual in addition to monolingual thesauri in a single document, monolingual taxonomists who read the ISO standard will broaden their awareness of the uses and possibilities of multilingual taxonomies, and that’s a good thing. On the other hand, a standard that appears from its title to be just about “thesauri” is likely to be overlooked by taxonomists who work with other kinds of controlled vocabularies.

The importance of the standards should not be overlooked. Taxonomies are only useful if they are well constructed, and decades of experience, practice, and use have indicated the conventions by which the most usable and useful taxonomies should be built. In addition to prescribing what works, the standards also encourage consistency. Consistently designed taxonomies thus become familiar to users, who then know how to use them with minimal training. Users don’t have to be told what a narrower term is and where to find it, or what a related term is and what its purpose is.

Taxonomy or thesaurus standards are a particularly useful resource to taxonomists. Other information management standards (such as for cataloging, indexing, bibliographic citations, etc.) have been reproduced, republished, disseminated, etc. by numerous professional organizations, nongovernmental institutes, educational institutions, and in numerous books. There is no need for the average information professional to look up the original, primary source standard. Taxonomy construction, however, is not such an established discipline or activity. In the field of taxonomies, professional membership organizations are lacking (except for divisions or special interest groups of larger organizations), academic courses are merely nonstandard electives, and books are fewer. The nature of the free-for-all style of the web, which is the platform for most taxonomies today, also poses challenges to conformity in style. Therefore, there is in fact a greater need for the average taxonomist to consult the original, primary source of standards.

For most individual taxonomists, I would suggest that the ANSI/NISO standard is sufficient, and there is no need to also read the ISO standard. However, for an organization or enterprise engaged in taxonomy building and implementation, the additional ISO standard is probably a good investment. Finally, any taxonomist involved in teaching or consulting would also find the ISO standard a valuable additional resource.


  1. This is a great post Heather. I feel the urge to re-read the ANSI/NISO standards!

  2. In a comparison of ANSI/NISO Z39.19 with ISO 25964-1, it is fair to mention a good degree of compatibility, but I would have expected more indication of the extra scope in the international standard - especially given today's demand for interoperability features. For example, the standard provides a data model and XML schema for data exchange, all available 24/7, free of charge at . The latest issue of NISO's magazine "Information Standards Quarterly" has an article about the evolution of both standards at . Also helpful is Leonard Will's article "The ISO 25964 Data Model for the Structure of an Information Retrieval Thesaurus", in the April/May 2012 ASIS&T Bulletin, at .
    Happy reading!
    Stella Dextre Clarke

  3. Has there been a ANSI/NISO standard or any sort of guideline on multilingual vocabularies published? I cannot find one that fits on the ANSI/NISO website.

  4. If we build the foundation of our taxonomy based on ANSI/NISO, will we be totally adrift if asked to incorporate ISO in the future?

  5. Not at all. ANSI/NISO and ISO are fully compatible. The difference is in scope. For example, ANSI/NISO does not include guidelines for multilingual thesauri, whereas ISO does, but that does not meant the guidelines for monolingual thesauri are different. It's a matter of an extension/additions.