“A good ruler has to learn his world’s language, and that’s different for every world, the language you don’t hear just with your ears.” – Frank Herbert, Dune

Synonymy

Synonyms are “one of two or more words or expressions of the same language that have the same or nearly the same meaning in some or all senses” (Merriam-Webster). We can define synonyms when building taxonomies using the skos:altLabel field from semantic standards created by the W3C. The W3C defines skos:altLabel as “an alternative lexical label for a resource”, which, using the same words in the definition as in the label, isn’t as helpful as their example: “acronyms, abbreviations, spelling variants, and irregular plural/singular forms may be included among the alternative labels for a concept. Mis-spelled terms are normally included as hidden labels (see skos:hiddenLabel)” (W3C).

Synonymous concepts are part of what make taxonomies complete, clear, and demonstrate a consideration for each selected concept distinguishing between the chosen preferred label, the possible other languages for that preferred label, and other possible options which can be captured in the altLabel field. English may or may not have the most synonyms, but it certainly has many:

“The richness of the English vocabulary and the wealth of available synonyms means that English speakers can often draw shades of distinction unavailable to non-English speakers. Modern English has an unusually large number of synonyms or near-synonyms, mainly because of the influence of very different language groups: Germanic (Anglo-Saxon and Old Norse, the main basis of English), Romance languages (Latin, French), and Greek. There are many sets of triplet synonyms from Anglo-Saxon/Latin/Greek and also Anglo-Saxon/Norman French/Latin-Greek like cool-calm-collected and foretell-predict-prophesy” (Why other languages don’t use thesauruses like we do).

Synonymy is not as cut and dried as it would seem. Let’s consider the use of the skos:altLabel in practice.

ALTruism

According to the W3C, the altLabel field can, by definition, include acronyms, abbreviations, spelling variants, and even irregular plural or singular forms. If we use the “out of the box” set of SKOS labels, it simplifies the structural encoding of taxonomies and reduces the number of properties we need to maintain and manage. However, just as synonyms aren’t purely objective, there are a few disadvantages and risks involved with only using the skos:altLabel. First, the nuanced differences between acronyms, abbreviations, and spelling variants is lost. Second, the ability to separate these nuanced differences in systems consuming altLabels from a taxonomy and ontology management system becomes difficult, if not impossible. Finally, taxonomy consumers or viewers may or may not know what an altLabel is, what it includes, or why the values they are seeing in that field seem to differ.

Defining separate, clearly named taxonomy properties defined by the skos:altLabel type may help to solve this problem. Let’s consider a few examples.

Synonyms

Using the skos:altLabel field type but naming it synonym can make it clear for end users what values to expect. A field like this could include “true” synonyms like “shoelace” and “shoestring” and synonyms which an organization defines for their domain, like “footwear” and “shoes”. These are not truly synonymous, but for an organization which sells footwear of all types, they might be.

Acronyms

Acronyms may be a clearer example since an acronym is more narrowly defined. Even here, it depends on the taxonomy use case, altruistically considering the audience. One organization may use the preferred label “deoxyribonucleic acid” while another organization may use the preferred label “DNA”. In either case, defining shades of skos:altLabel can help. In one instance, “deoxyribonucleic acid”” is the preferred term while “DNA” is included in the acronym field. In the other instance, “DNA” is the preferred label while “deoxyribonucleic acid” is in the synonym field. Using fields in this way very clearly expresses the organization’s viewpoint on how they approach the domain.

Abbreviations

Using skos:altLabel as an abbreviation field also sets expectations for what is included. I live in California, and when I abbreviate the state name, I use “CA”. I remember, however, using longer state name abbreviations when I was younger (which is interesting, because the U.S. Post Office officially switched to two letters in 1963…and, well, I’m a little younger than that). In this case, we could include all of the historical abbreviations “Cal.”, “Calif.”, and “CALIF” in the abbreviations field.

Historical Label

If we want to add even more nuance in naming a skos:altLabel field, we could include something like historical label, more or less paralleling the skos:historyNote field. Using another California example, the historical label field could include “Oakland Raiders” and “Los Angeles Raiders” for the team “Las Vegas Raiders”. These terms are really synonymous, but we’ve added another layer of clarity by adding a time element. If a taxonomy and ontology system supports adding metadata to properties and relationships, you could use the synonym field and add date ranges for when the team was active with each name: “Oakland Raiders” (1960-1981, 1995-2019) and “Los Angeles Raiders” (1982-1994) with the option to add an open date range to “Las Vegas Raiders” or no date range at all.

Spelling Variants

The use of skos:altLabel for spelling variants is dependent on your use case, in my opinion. For taxonomies supporting search, it may be valuable to define a field called spelling variant. Likewise, despite W3C’s recommendation, there could be another field called misspellings. However, in practical application, maintaining spelling variants and misspellings is the work of the front-end search system, not the taxonomy. How you architect your taxonomy to support search may be a matter of your organization’s technical environment, so do what’s best for your use case.

Another Word for Thesaurus

You’ve probably heard the old joke, “What’s another word for thesaurus?” Well, the slippery nature of language is on display in that the Merriam-Webster online dictionary provides seven “Synonyms & Similar Words” for “thesaurus”. So, the answer is: dictionary, gloss, glossary, lexicon, nomenclature, vocabulary, or workbook. All of these, arguably, are not synonyms for the word “thesaurus”.
I’m not going to get into homonyms, homographs, or the use of the skos:closeMatch or skos:exactMatch relationships in this blog because, although all are similar concepts, they are not synonyms. What I will leave you with is adhering to the W3C standard is a good practice in taxonomy and ontology design, but creating nuanced flavors of the skos:altLabel might prove to be a useful alternative for your taxonomy audiences.