Taxonomy is a confusing word that usually conjures up images of complexity and often feels like a baffling concept used only by the erudite. What are people talking about when they mention taxonomy in the information architecture(IA) field? And how is it different from the organizational systems in IA?
Join me as we embark on a quest to unravel this concept!
What is Taxonomy?
The definition
A taxonomy is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. Among other things, a taxonomy can be used to organize and index knowledge (stored as documents, articles, videos, etc.), … so that users can more easily find the information they are searching for.
-Wikipedia definition
Referring to Heather Hedden’s book “The Accidental Taxonomist”, the word “Taxonomy” is rooted in two Greek words: taxis meaning arrangement or division, and nomos meaning law or science.
And for present-day information management, the term taxonomy is utilized in both a narrow and a broad sense. In a narrow sense, it means a hierarchical classification or categorization system.
This scope of taxonomy is common in the life sciences domain (See the example below). Taxonomies are used to classify animals based on shared characteristics. Animals are typically classified in a hierarchical manner which includes both superior and subordinate categories with well-defined vocabularies such as “species”, “Genus”, etc.
By doing this, scientists can locate, and retrieve information more easily in a consistent system and sometimes the correlation between each information piece becomes more apparent.
However, Heather Hedden also notes in her book that the use of taxonomy extends beyond its typical scope, serving broadly as a method for organizing concepts of knowledge. This broader application equates taxonomy to a knowledge management system.
For example, in the context of digital environments, taxonomies are utilized to systematically categorize digital content on a website into topics and subtopics. More specifically, libraries typically employ taxonomies to sort books and resources under genres or subgenres such as “History”, “Fantasy”, “Biography” and others. Such categorization aids users in finding, retrieving, and interacting with information on the website and also supports the website’s consistent growth and adaptation.
*Notes: A taxonomy is not necessarily to be hierarchical, there are other kinds and displays of taxonomies such as facet, attribute-oriented, and more.
Controlled vocabulary
When we talk about taxonomy, you will find the word “controlled vocabulary” always comes with taxonomy. What’s the relationship between these two terms?
Let’s make it simple, a taxonomy is just a type of controlled vocabulary — a list of words or terms for specialized purposes. It is “controlled” because only terms from the list may be used for the subject area covered. Therefore it ensures that everyone — your team, your stakeholders, your users — is using the same language and definitions throughout the experience.
*That’s why sometimes a taxonomist call themselves controlled vocabulary editors!
Now, let's conclude it in the easiest way, a taxonomy is a closed list of carefully selected terms/vocabularies that are usually arranged in a hierarchical order to describe and classify content so that it can be retrieved effectively.
How is taxonomy used in IA design?
Tags
Taxonomies are complex beasts, far more elaborate than “just” tags. I have no intention of undercutting their true nature — but for many designers (and users), tags are the most immediate and concrete application of taxonomy.
-Lisa Maria Martin
Tags are metadata that is attached to subjects or contents. When you add a tag to something, you’re basically giving it a label that briefly describes what it’s about or its nature. This process not only adds context and meaning to the subjects but also facilitates the retrieval of it and its connection with other related subjects.
For example, in the tags example below, the helium balloon can be tagged with “pink”, “light”, “helium”, “flying”, and all other words that can be used to describe it.
Tags can enhance content by allowing it to be categorized by narrowed attributes rather than by general rigid groupings. Such flexibility is essential for search engines, which rely on these tags to better understand the content and index them effectively, therefore people are more likely to find it when they search online.
Facet Search
Taxonomy can be also used for faceted search, which allows users to explore a collection of information by applying multiple filters simultaneously without browsing all the content. Facet taxonomies, often organized in hierarchical trees (or several hierarchical trees), enable users to start with broad categories and narrow down to more specific topics. By selecting various facets derived from the taxonomy, users can refine their search to locate exactly what they need, whether they’re shopping online, searching a library catalog, or navigating a database.
For example, on this online shopping website, users can find what they want to buy based on the main categories (clothes, shoes, accessories, etc), but also more detailed attributes such as color, sports & activities, Athletes, materials, etc. This kind of facet research is supported by a rigorous facet taxonomy.
Search Suggestion
Taxonomies can aid in search suggestions, streamlining the user experience by predicting and offering relevant options based on the hierarchical classification it contains.
For example, when you type “shoe” into Amazon’s search field, a pre-structured taxonomy might suggest “shoe rack,” “shoe organizer,” or “shoe cleaner” to anticipate the user’s needs, making the search easier.
Similarly, taxonomies are useful when content is accessed by various users who may describe things differently. Because a taxonomy can help connect synonyms or related terms to the user’s search intent.
For instance, searching for “running shoes” on the REI website may yield results for “trail-running shoes,” “road running shoes,” or “cross-training shoes,” making a wider range of related content more visible and accessible to users.
What’s the difference between the Organization System and Taxonomy?
The organization system is one of the most important systems in IA. It refers to the methods and processes used to arrange content and information in a way that is logical and understandable to users. The goal of an effective organization system is to align with users’ mental models — their expectations and understanding of how the information should be organized — so they can find what they’re looking for with minimal effort.
For example, we will categorize strawberries, melons, cherries, and bananas into the folder of “Fruit,” because it will create an intuitive and user-friendly way for people to find and identify these items as fruits within this group.
A taxonomy, on the other hand, is usually a tree structure of controlled vocabulary that we use to describe or tag our content/information and how all this information relates to one another. Therefore it feels more like a backend technical thing instead of an organization system that users would frequently interact with. And as we describe in the prior section, taxonomies usually contribute more to an exact search system.
Returning to the fruit example, while an organization system may group items under a “Fruit” category, a taxonomy could further delineate this into subcategories like “berries,” “melons,” and “tropical fruits,” or even based on taste or texture, such as “juicy,” “soft,” or “crisp.” This allows users to discover more specific results within these subcategories.
And remember it’s OK for you to still feel a little bit confused about all these concepts, as an IA designer you will gradually figure it out along the way!