Source: Dreamstime

Which quiche? You’ll have to read to the end to find out.

As many of our readers are aware, hierarchical thesauri are distinguished from other taxonomies by (among other things) the inclusion of non-hierarchical relationships among terms. One main type of non-hierarchical relationship is the equivalence relationship, which is usually expressed as a preferred term – non-preferred “term” (generally a synonym or quasi-synonym) pairing. The other main type of non-hierarchical relationship is the associative relationship, in which regular thesaurus terms are paired. (Note: I’m using “regular terms” here to refer to what are commonly called “preferred terms”, meaning terms that aren’t non-preferred terms.)

The paired terms are called “related terms”; while terms in a thesaurus can be “related” in various ways, “related terms” are those that carry a reciprocal associative relationship. If Term A has Term B as a related term, then Term B will likewise have Term A as a related term. Good taxonomy management software will be responsive to a taxonomist’s addition of a related term to a term record, and will automatically add the reciprocal relationship to the other term’s term record.

The Z39.19 standard (ANSI/NISI Z39.19-2005 (R2010), “Guidelines for the Construction, Format, and Management of Monolingual Controlled Vocabularies”) offers a somewhat vague definition of the associative relationship: “A relationship between or among terms in a controlled vocabulary that leads from one term to other terms that are related to or associated with it.” (Subsection 4.1) As the standard comments later (8.4), “the associative relationship is the most difficult one to define.”

Subsection 8.4 does capture the essence of the associative relationship: “This relationship covers associations between terms that are neither equivalent nor hierarchical, yet the terms are semantically or conceptually associated to such an extent that the link between them should be made explicit in the controlled vocabulary, on the grounds that it may suggest additional terms for use in indexing or retrieval.”

Z39.19 discusses associative relationships between sibling terms, as well as the more common (and perhaps more valuable) associative relationships between terms in different hierarchies within a thesaurus. With the sibling relationships, the conceptual relationship should be stronger than simply being part of the same broader concept; otherwise, there is no point in adding the associative relationship. (I should point out here that there are those who advocate for always adding associative relationships among sibling terms.) Even so, when one browses or navigates a thesaurus, siblings are readily visible. The value of associated siblings is mainly in search.

Associative relationships across hierarchies are another matter. They call attention to terms (and content indexed with those terms) that the thesaurus user or searcher should perhaps be aware of, and otherwise might miss. Some of the example pairings in Z39.19 are weaving and cloth; pathogens and infections; surface tension and liquids; and ducks and rubber ducks. These examples are from Z39.19’s Subsection 8.4.2, which illustrates the various types of associative relationships (such as Process / Agent) listed in a table in section 8.1. While it’s instructive to be acquainted with these types, there’s no need to memorize them or refer to them, unless one is looking for inspiration for adding more “related terms” to a term.

Here are some of the problems I’ve seen with related terms in thesauri:

Few or no related terms; not taking advantage of the ability to add related terms, and missing out on the benefits that they can provide.

Too many related terms, with the ones that could be valuable getting lost in the mix, and the network of relationships becoming cumbersome.

Very vague related terms, with no real value. This often goes hand in hand with too many related terms.

Related terms that might better serve as broader or narrower terms, in a hierarchical relationship.

And last but not least, terms that would be great as related terms, but that are in an inappropriate hierarchical relationship.

One simple example of the last problem has to do with quiche. As mentioned elsewhere in the TaxoDiary blog: “In a food thesaurus, “Quiche” or “Quiches” would not be appropriate as a narrower term under “Vegetarian foods,” because some quiches contain bacon or ham.”

However, Quiche would make a fine related term for Vegetarian foods, because many quiches are suitable for vegetarian consumption.

So choose wisely, and Bon appetit!

Barbara Gilles, Communicator
Access Innovations, Inc.