You may often hear the terms “classification” and “taxonomy” used interchangeably. While these concepts share some similarities, there are also significant differences and have distinct meanings in the world of user experience.
What is a taxonomy?
A taxonomy is a knowledge organization system, where terms are hierarchically related. It focuses on specific terms needed for tagging or indexing content, rather than dividing a domain into classes and subclasses.
The word “taxonomy” comes from the Greek words “taxis” (arrangement) and “nomia” (method). Taxonomy has a rich history, often associated with the field of biology’s categorization of living organisms by Carl Linnaeus in the 18th century. In UX, the term evolved from library sciences, where organizing information is a crucial aspect of the work.
The Nielsen Norman Group describes taxonomies as controlled vocabularies — “planned, prescriptive ways of adding descriptive metadata to content so that it can be retrieved effectively.” Author Page Laubheimer continues:
“The idea is that the taxonomy defines a limited set of terms for describing our content in the background; content creators must attach them to any new piece of content, with no ability to expand this vocabulary on an ad hoc basis.”
A controlled vocabulary in taxonomy emphasizes concepts rather than specific items. It organizes terms in natural language order and is designed for “post-coordination,” combining terms at the time of a search query.
Taxonomies are designed for tagging and indexing, not for classification or cataloging. The focus is on identifying the main topics of documents.
The taxonomy view is hierarchical, showcasing broader terms, narrower terms, and top terms. A taxonomy can be considered a map of concepts one uses to describe their content, and how all of those concepts relate to one another, Page Laubheimer writes.
The essence of taxonomies lies in the connections between concepts through parent-child relationships. The deeper into a taxonomy, the finer the distinctions.
Why use taxonomies in UX?
Taxonomies help make information accessible, enabling efficient navigation and searchability. They can allow for dynamic search suggestions — i.e., as a user types in a search field, the search functionality can refer to stored taxonomy, pulling results from similar terms.
In the specific context of websites, taxonomy serves as the organizational structure, arranging content logically to facilitate user navigation and comprehension of the site’s purpose.
Various types of website taxonomies cater to different organizational needs.
- A flat taxonomy, suitable for smaller websites, comprises a simple list of top-level categories. A flat taxonomy might be best for a blog with a simple list of topics.
- In contrast, hierarchical taxonomies, common in larger websites, arrange categories by order of importance. A hierarchical taxonomy might best serve a large e-commerce site.
- Network taxonomies organize content into associative categories with meaningful relationships.
- Faceted taxonomies allow topics to be assigned to multiple categories, facilitating content discovery through specific attributes. A faceted taxonomy comprises multiple separate taxonomies, each hierarchical in nature, integrated to delineate various facets of a shared resource. As the Nielsen Group notes, The Library of Congress uses a faceted search on its digital collections page to help users filter down results.
What is classification?
Classification, meanwhile, refers to the systematic grouping of items by one or two shared characteristics. Classifications are generally not hierarchical. They are used to create meaningful clusters that enhance user comprehension.
“Classification” has the Latin root “classis,” which means class or division. Classification can be seen in Aristotle’s work on organizing knowledge. In Categories (part of Organon), Aristotle describes a “fourfold classification of things that are.”
While taxonomy aids in establishing a structured framework for content retrieval, classification proves beneficial in forming adaptable and user-friendly groups.
In UX, a task management app could use classification to group one’s tasks based on status or project, simplifying a user’s interaction with the app.
What makes taxonomy and classification similar, and different?
Even though taxonomy and classification help organize information, they have different approaches to doing so. Taxonomy emphasizes hierarchical relationships and controlled vocabularies for tagging and indexing, supporting efficient content retrieval. Meanwhile, classification creates groups based on shared characteristics to enhance user understanding.
Where to use taxonomies vs. classification?
In the UX world, understanding these differences is crucial for creating straightforward and user-friendly information structures.
Taxonomy can be useful in situations where a clear hierarchy and structured organization are critical. For instance, an online shopping site like Amazon, which uses deep hierarchies for product categories to aid user navigation — or a knowledge base like Wikipedia, which uses taxonomy to organize its articles into subject areas to help users discover content. It is important to be aware that taxonomies have the potential to become challenging to modify if there are frequent content changes.
Classification is useful where the volume of content is moderate, and where grouping based on shared characteristics is key–as in a photo-sharing site that allows users to group photos into broad categories based on the photo’s subject, to make using the service easier. Classification systems are more adaptable to regular updates.
By using taxonomy for structured organization and classification for meaningful clusters, designers can improve the overall user experience and make content navigation more effective.
