How to Teach Taxonomies

On several occasions   Heather Hedden, one of our authors,  gives full-day workshops on how to create taxonomies and other controlled vocabularies, and it’s interesting how different issues or problems arise in different sessions. It may be just one individual who has difficulty grasping a concept and asks lots of questions, but in answering the questions, it turns out that others have similar questions. It then becomes apparent that some principles, while simple on the general abstract level, can get muddled when we start looking at specific examples.

Here are Heather’s strategies that she’s  learned to help train new taxonomists in building taxonomies:

1. Use different methods of explanation to serve different backgrounds and mindsets

In one session I gave, an exercise on creating correct polyhierarchies had some people perplexed. The exercise was to propose two or more broader terms for “Paint Brushes.” Had I asked the participants to suggest just a single broader term, I probably would have gotten mostly correct answers, such as “Painting tools” or “Brushes.” But when having to propose two broader terms at once, many taxonomy students had gotten off-track and proposed a pair such as “Artists tools” and “Contractors’ tools.” This, of course, is not correct, since not all paint brushes are used by artists, and not all paint brushes are used by contractors. In one session, several minutes of attempted explanation to one individual were insufficient.

For the trainees who are more mathematical, an analogy with Boolean logic might make more sense. In such a case, we can say that the polyhierarchy represents the Boolean AND, rather than OR. The narrower concept must always belong to both Broader Term A AND Broader Term B, and thus the narrower term in a polyhierarchy represents the intersection or union of its two broader terms. For others with a reference searching or indexing background, however, it is necessary to explain the search and retrieval implications of the hierarchy. For example, “Paint brushes” is a term indexed to documents on all kinds of paint brushes, including those for commercial exterior painting. Thus, it would be incorrect to retrieve the latter documents with the broader term for “Artists’ tools.”

2. Teach the standards in the most practical sequence

At a recent corporate training I gave, the topic that was most challenging for the participants was associative relationships. The specific issue was what kinds of term pairs could legitimately use this kind of relationship. Listing all the possible types of term pairs for associative relationships as described in the ANSI-NISO Z39.19 standard (13 of them!) can add more confusion than needed. Training participants wanted to refer to this list when completing an exercise on proposing related terms. As a result, they proposed some rather unconventional related terms, that, while legitimate, were not entirely practical.

Teaching principles from the ANSI-NISO standard, I realized, should not necessarily rely on the same sequence or emphasis as written in the standard. It is probably better to present the list of 13 associative relationship types at the conclusion of an explanation on the associative relationship, rather than at the beginning. Similarly, I found that the ANSI-NISO standard’s order of presenting relationships between terms belonging to the same hierarchies followed by term terms belonging to different hierarchies may also not be best, since relationships between terms belonging to different hierarchies are more common.

3. Simplify demonstration exercises

Setting up a practice card-sorting exercise for classifying things can be a part of training session, but the card-sorting exercise should be modified. I had attempted once to create a number of cards (at least 25) considered desirable for a card-sorting exercise, only to find that the training participants only want to spend a few minutes on it, rather than the more intense 10-20 minutes that actual card-sorting participants would be expected to devote. Thus, a demonstration card-sort should be a much small set, along with the clear statement that an actual card-sorting exercise would be larger.

4. Revise sample exercises

Finally, the exercises included in training workshops may need to be tweaked after they are tried out. For example, asking for suggested broader terms for the term “Financial Management” obtained such varied and questionable results, that I had to remove that example and replace it with another. What I had in mind as broader terms were quite simple “Finance” and “Management,” but my audience was looking for other, more specific meanings of the term. Examples should not be ambiguous.


Even if you are not a professional taxonomy trainer, a lot of training is needed in the taxonomy field, and a lot of people learn how to create taxonomies on the job. Thus, if you are a taxonomist, you may find yourself required to teach taxonomy principles to others. Although some of it may come naturally to you and those you teach, other taxonomy principles will be more difficult to teach, and creative strategies are needed.

– Heather Hedden

Heather can be contacted for more information about her workshops and upcoming presentations at  Hedden Information Management.