Navigation Schemes vs. Taxonomies

A navigation scheme for a website/intranet and a taxonomy are similar, but they are not the same. I had taken an interest in website information architecture, around 16 years ago, about the same time that I became familiar with the term “taxonomy” (although I had already been working for years as a “controlled vocabulary editor”), so I naturally related website navigation and taxonomy. In an earlier version of the online course I teach on taxonomies, I had even presented examples of website navigation schemes as examples of taxonomies. However, I also recall hearing early on in conference presentations of the consultant Seth Earley that a navigation is not a taxonomy. After more years of experience with taxonomies, I came to recognize that as true. Considering a website navigation structure as an example of a taxonomy is an oversimplification and could lead to poor taxonomy design.

I looked more closely into the comparison of website navigation and taxonomies in preparation to present at World IA Day Boston on February 22 (presentation slides PDF, presentation video). IA stands for information architecture. So, now I will continue with that line of observations here. This topic also follows another example of what a taxonomy is not. It is not a classification scheme, which I also discussed in a recent blog post, “Classification Systems vs. Taxonomies.”

A navigation scheme is typically presented as a set of menus and submenus and possibly also a supplemental site map, although the latter has become far less common on websites than it used to be. The navigation scheme of a website, intranet, or portal reflects the structure of the content, which has been designed in a way to serve various sets of users (defined by generic “personas”) with various common kinds of tasks, such as finding people, reports, events, office locations, financial data, etc., submitting requests, providing feedback, and placing orders, among others.

The one area where navigation and taxonomy may overlap is in a website where the content is entirely publication-like articles or documents. In this case, the site navigation is just for finding articles or documents based on their subject matter, so a topical taxonomy for indexing and retrieving documents may appear as the navigation menu for the site.  This is the case for news media sites, for example.

With a background in indexing, I like to compare the index of a book with the taxonomy-enhanced search capabilities of a website, whereas the table of contents of a book is like the navigation scheme. A table of contents or navigation scheme is a higher-level, pre-defined structure of content, that guides users to the general organization of content and tasks. It helps users understand the scope of the content available, provides guidance on where and what content to find, and aids in exploration. An index or search feature, including faceted search, on the other hand, enables to user to find specific information or content items of interest. A taxonomy, regardless of its display type, serves the function of an index, not the table of contents. I have also compared taxonomies with tables of contents in a blog post several years ago, “Taxonomies and Tables of Contents.” 

Even when a taxonomy is hierarchical, it differs from a navigation scheme or table of contents, because it is an arrangement of terms/topics/concepts. By contrast, the navigation (or table of contents) is an arrangement of named content (named pages/sections, etc.). This is key. Terms, topics, or concepts (the distinctions between which are beyond the scope of this discussion), while reflecting the content of the website or intranet, are somewhat generic, can apply to any content in the site, and whose meaning should  be understood independent of the location in taxonomy hierarchy. Think of the tagging aspect of taxonomies.  Any hierarchy that the taxonomy terms are arranged in reflects the meanings of the terms and the relationships of the terms to each other. It does not reflect the arrangement of the content. Navigation menu labels, on the other hand, are short descriptions of pages or sections (with landing pages), which they match one-to-one, and the hierarchy of the menu reflects the hierarchical structure of the content.

The following table lists the various differences between navigation schemes and taxonomies.

Navigation schemes	Taxonomies
Single-site use and implementation	May be re-used in multiple implementations
Reflect the site-map structure	Reflect organic relations of the topics/concept
Labels based on page titles	Labels based on concepts/topics
Designed to be browsed hierarchically, top-down	Designed to be browsed, searched, or may not be fully displayed to users
2-3 level hierarchy limit	Options for deeper hierarchy and/or facets
One-to-one label-to-page	One-to-many label to multiple pages
Do not include or link to all pages	Cover all pages or content
Limited in size	Can be small or large
Biased to emphasize what is important	Neutral to topic importance
Not so flexible for updating	Can grow and adapt without limits
Have paths and links, not metadata	Concepts are often metadata

What may be confusing is if we think of taxonomies purely has hierarchical structures and thus equate them with navigation schemes, which are also hierarchical. The feature of being hierarchical does not make something a taxonomy, as I explained in the “Classification Systems vs. Taxonomies.”  Although a taxonomy may be hierarchical, there are other kinds and displays of taxonomies. Taxonomies may be fully displayed for browsing as hierarchical or alphabetical, displayed in excerpts in facets, displayed as short lists of terms in type-ahead or search-suggest features, or not displayed at all as a search thesaurus (also called a synonym ring).  The idea that taxonomies do not have to be hierarchical will be the topic of my next blog post.