Taxonomy Trends

Last fall I gave an 8-minute video presentation as part of the SEMANTiCS Video Forum 2020 on the subject of taxonomy trends, but the short talk allowed time to discuss only two of the past year’s trends. More recently, I reflected on longer-term trends in taxonomies when the chair, Jane Dysart, of Computers in Libraries conference suggested that my pre-conference taxonomy workshop last month also include the what’s new with taxonomies and assigned me the workshop title “Taxo Update: Latest in Designing & Maintaining Taxonomies.” While, by their nature and purpose, taxonomies should remain somewhat consistent in their design, I came up with some ideas in various sections of the workshop presentation.  Now that the event is past, I’ve collected my observations of taxonomy the trends that I included in that workshop.
 

Convergence of types

A trend in the broader realm of knowledge organizations is the convergence of different types. We are seeing a convergence of taxonomies and thesauri, which is due to factors including the widespread adoption of the SKOS (Simple Knowledge Organization System), which supports both taxonomies and thesauri fully. Vocabulary management software, which is becoming more widely adopted than just using spreadsheets or the basic taxonomy editing feature of a content management system, supports both taxonomies and thesauri with no distinction. There may also be a growing preference to have the features of both: a dominating hierarchical structure as in taxonomies, and the benefit of additional associative (non-hierarchical) relations as supported in thesauri.

There is also a convergence of taxonomies and ontologies. This is also partly due to software tools, such as PoolParty, that support both taxonomies and ontologies in an integrated manner. There is a growing interest in ontology features, such as semantic relations and custom attributes, without having a large complex ontology, so a simple ontology can be applied as a semantic layer to existing taxonomies. This brings up the fact that there are growing number of taxonomies in existence that can be utilized within an ontology, rather than being replaced by an ontology. Finally, there is an increasing interest in ontologies as they form a basis of knowledge graphs, which are becoming more popular.

Interest in standards

In the past, the focus on taxonomy-related standards was mostly on ANSI/NISO Z39.19 Guidelines for the Construction, Format, and Management of Monolingual Controlled Vocabularies and its related ISO standard, ISO 25964 Thesauri and interoperability with other vocabularies. Their emphasis on best practices for thesauri has perhaps limited these standards somewhat in their broader application to taxonomies. More recently, however, there has emerged a greater interest in interoperability of taxonomies and other controlled vocabularies, which is recognized and addressed the second part of ISO 25964.

Even more significant is the is the increased adoption of SKOS and other W3C (World WideWeb Consortium) guidelines and recommendations, which directly support interoperability and exchange and sharing of vocabularies. As the number of taxonomies and other controlled vocabularies grow, there is a greater interest in re-using parts of them, sharing them, and linking them, which is enabled by representing the data in a standard format. The SKOS model can also be expressed in RDF (Resource Description Framework) triples, which makes it suitable for general Semantic Web sharing and linking, whether on the web or behind the firewall with Semantic Web standards. SKOS has also become the standard supported by most taxonomy management software.

Besides supporting interoperability, another trend coming out of SKOS is a shift in thinking of terms to that of concepts.  Terms are strings of text, but concepts are ideas that may have various labels. Thus, people talk about “things, not strings.”

As for the standards for taxonomy and thesaurus best practices design, ANSI/NISO Z39.19 is not forgotten but rather there is sufficient interest in the taxonomy community to review and revise this standard again soon. I expect work on that to start in late 2021 or early 2022, and I hope to be involved. I will report more on that in a future blog post.

Trends in taxonomy structural design

In hierarchical taxonomies, there is the trend that hierarchies are created increasingly for purposes other than fully displayed for end-user browsing. Traditionally, the hierarchical design structure of taxonomies was solely for the purpose of serving end-users who would be browsing and need guidance in going from broad categories to narrower topics. The associative (related term or see also) relationship also guides users who are browsing and those who are doing manual indexing/tagging to identify related concepts of interest. As fully browsable taxonomies are becoming less common (due to their growing size and the availability of alternative methods of search and findability), and more indexing is automated, hierarchical and associative relationships between concepts are less often implemented to support browsing, and are more often used so support auto-tagging, providing context for a concept’s meaning by the presence of broader and related concepts.

When the relationships between concepts are not displayed to end users, the taxonomy structure does not necessarily need to be as consistent, such as always having a set number of hierarchical levels in all places of the taxonomy. A taxonomy does not have to appear as complete and comprehensive, either, but rather it merely represents the content. Associative relationships between concepts may also be implemented more inconsistently. This is another factor that contributes to the convergence of taxonomies and thesauri, since by definition thesauri have associative relationships and taxonomies do not. But you may end up creating a taxonomy/thesaurus with just a few associative relationships.

Despite the trend of less fully displayed hierarchical taxonomies, there are still many taxonomies that are fully displayed, such as in ecommerce applications. A growing trend is to combine different methods of expanding form one level to the next between different levels of the same taxonomy. There is also more sophistication integrating both common and custom facets into different levels of a hierarchy.

Trends in uses

Last, but certainly not least, is the trend in wider adoption of taxonomies for various uses. This was the topic of my prior blog post, Industry Uses for Taxonomies.