Taxonomy and Information Architecture Compared

There is considerable overlap between the fields of information taxonomies and information architecture. Both involve information organization, labeling, search, and findability. In some organizations the job roles and titles are combined. I previously blogged on “Information Architecture and Taxonomies,” observing that “information architecture” in name seemed to be declining while aspects of its practice continued to be strong, since it was an underlying theme in several of the talks at major taxonomy conference, Taxonomy Boot Camp in 2013.

Information Architecture Conference opening. Photo Marisela Meskus

This week, for the first time, I am attending in person the Information Architecture Conference, being held in New Orleans March 28 - April 1, so it’s been interesting to hear how information architects consider taxonomies.

How Information Architecture and Taxonomy Overlap

The fields of information architecture and taxonomy are related beyond the stated shared practices of information organization, labeling, search, and findability. 

When I give an introduction to taxonomies, I explain that a taxonomy is an intermediary between users and content to connect users to content by means of terms that the users understand and by the display of the terms in hierarchies, facet-filters, or type-ahead suggestions, which enable users to explore and interact with the taxonomy. This is clearly an aspect of information architecture. 

In my own career path, I discovered taxonomy and information architecture at the same time. I had been working as a “controlled vocabulary editor” and had the opportunity to work on an interdisciplinary team for a newly design information product. A user interface for school library research database included both a hierarchical taxonomy that was designed to fit with a particular user interface. 

At the Information Architecture Conference, I asked for a raise of hands of my session audience of how many had worked with taxonomies, and it seemed to be over 80%. At the conference, I met information architects who specialized in taxonomies, and taxonomists who had an interest and done some work in information architecture. Even though I identify as a taxonomist, I already knew a number of speakers at the Information Architecture conference due to the overlapping communities.

How Information Architecture and Taxonomy Differ

Information architecture is a discipline and a profession that is larger and more established than that of taxonomies. Although taxonomy work is growing, there are still more college courses on information architecture than on taxonomies, more books on information architecture than on taxonomies, and more people with “information architect” than “taxonomist” as a job title (based on LinkedIn searches). 

Listening to sessions at the Information Architecture Conference and having discussions with participants, I began to see a clearer picture on how the fields of information architecture and taxonomies differ.

The Information Architecture Conference brings together a community of professionals who share ideas and experiences. There is no comparable taxonomist community as taxonomy work, compared to information architecture work, tends to be done by those with different professional backgrounds: information architects, librarians, content managers, metadata architects, indexers, ontologists, etc. It’s telling that there is not just one conference at which I present about taxonomies but multiple. (Knowledge management, content strategy, knowledge graphs, and data science are the fields of conferences at which I have spoken about taxonomies in the past year.) The only conference about taxonomies, Taxonomy Boot Camp, is more of specialized track within the KM World conference, and aims to provide taxonomy best practices and case studies to managers and directors of content, product, or knowledge management. It is not really a forum for taxonomists to discuss topics of their profession, as the Information Architecture Conference is.

It seems that information architecture is more of a discipline and a field, whereas taxonomy is more of tool or system (although a very important one). In addition to information architects in organizations in various industries and consultants, the Information Architecture Conference includes professors and students in the field. By contrast taxonomy is not a field of study, research, or focus in academia. It is a focus area only in industry and consulting. Information architecture seems to allow more room for theory than does the taxonomy field. 

How Information Architecture and Taxonomy Are Related

From a "taxonomic" perspective, which is broader? For information architects, taxonomy is narrower than information architecture. There is no doubt that information architecture is broader in various ways, including content/information organization, design, user experience, and even organization of non-digital information spaces. For example, information architects are concerned not only with taxonomies to support searching and browsing for information, but also with content organization and navigation menu structuring in websites and in software user interfaces. 

Taxonomists, on the other hand, do not consider taxonomies as a sub-field of information architecture, but rather consider the two fields as adjacent and closely related. This is because the taxonomies that information architects create tend to be small, such as term lists for metadata properties or facets or as hierarchies to model menu navigation or site maps. Professional taxonomists tend to work on large dynamic taxonomies or thesauri that are used to tag/index and retrieve content or data in one or more systems, often where the user interface is already prescribed.

The related fields or disciplines are also different. Information architecture has a closer relationship with fields of design, user experience, sociology, and psychology. Taxonomy has a closer relationship with indexing/tagging, natural language processing, ontologies, Semantic Web technologies, and knowledge management. One related field shared by both information architecture and taxonomy is structured content, which was also a subject of presentations at this year's Information Architecture conference and the field of my next conference.

Taxonomies and Sitemaps

I was recently asked if a website’s sitemap of company’s website could serve as the start of a taxonomy for an organization. The sitemap, after all, includes all the relevant topics pertaining to an organization’s business offerings, and they are arranged in a hierarchy.  I have previously blogged on the subject of why a website’s navigation is not a taxonomy in Navigation Schemes and Taxonomies. A sitemap is similar to a website’s navigation, but it goes deeper by including the titles or topics of web pages which are not included in the website’s menu, and it is not necessarily intended for user browsing. A sitemap may go five or six levels deep, whereas the website menu navigation menus are usually only two levels. Therefore, a sitemap may seem as if it’s a taxonomy. However, just because a sitemap is as large and detailed as a taxonomy needs to be does not make it suitable as a taxonomy.

Different purposes

We need to understand what a taxonomy is for. It’s to aid users in locating desired content by topic-terms, which reflect both the terminology use of the users and of the content. Taxonomy terms are tagged/indexed to content that is relevant to the term. The starting point when creating a taxonomy is to identify the topics of the content and identify the topics of user interest or search, and then merge those topics into a taxonomy by bringing together different names for the same concept. The concepts are then structurally arranged to show the relationships between the terms, especially hierarchical relationships. The primary purpose of the hierarchy of terms in a taxonomy is to aid the users in finding the appropriate term. When browsing the taxonomy, they may find a broader term or narrower term that better describes their search goals. Then they can select that term to retrieve content that was tagged with the term.  

A sitemap, on the other hand, lists all or most pages of a website, usually by page title and organized in the hierarchical structure of the website. The hierarchical structure of the website was designed to organize information in a logical manner for users to browse and explore, as considered by the information architect who designed the website. The sitemap thus reflects pages, which are often topics but not always. A page may have multiple topics of interest that a user might want to look up. A page is sometimes for performing a function or activity and not necessarily just a topic of information.

A sitemap is typically automatically generated from the page titles, and its primary purpose is not for user but for machines: they tell search engines about pages that are available for crawling on websites and can thus support search engine optimization (SEO). Sitemap are useful in planning the further development or organizational improvement of a website. Whether a sitemap should even be displayed to end users as a tool to find information on a website is questionable. If automatically generated, it's not designed for that purpose, but users could find it helpful, especially users who understand that it is merely the aggregation of page titles organized in the file structure of the website. Some website make it available, and some do not. Some websites have displayed a simplified sitemap instead  that is designed to be a guide to the users, but then it do not include all pages.

Different labels

The title names of pages and thus of sitemap entries often do not correspond to taxonomy terms. They could start out with verb for an activity, they could be commands or questions, or they could be complete sentences. Taxonomy terms are topics or names only represented by nouns or noun phrases, or proper nouns. Examples of sitemap entries that are not good taxonomy terms may include:

How to use…
Get started with…
Help with…
Pay a bill
Shop for…

As with navigation, the entries of a sitemap reflect pages in a one-to-one relationship, in contrast to taxonomy terms, each of which may retrieve multiple pages or content sources, and each page or content item can be tagged with multiple taxonomy terms. As such, entries in a sitemap may actually be more specific than would be needed in a taxonomy.  The user’s selection of multiple taxonomy terms in combination, through filters/refinements, achieves the result of obtaining an appropriate list of relevant content.

Conclusions

Sitemaps should not be used as taxonomies, but their topics (not their labels) may be considered as a good source for a taxonomy. Sitemaps might not even be suitable as a basis or starting point for a taxonomy, but rather as a source for developing taxonomy terms. Rather, it is recommended that a taxonomy be created separately from a sitemap based on a review of content, search log data, and stakeholder and user interviews, and the sitemap is yet one other source for consideration when taxonomy terms. The hierarchy of the sitemap should also not be too closely followed, although parts of its hierarchical structure may be taken into consideration for creating taxonomy relationships.

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.

Taxonomies and Tables of Contents

A table of contents and a hierarchical taxonomy appear to be quite similar. In my last blog post I looked at taxonomies and indexes, and in the end concluded: “A taxonomy serves a purpose that is both, or something in-between, that of a table of contents and a back-of-the-book index. It’s for searching (like in an index) and also for navigating (like in a table of contents), but it points to the subsection level (as in a detailed table of contents), not to a page (as in an index).” Taxonomies, especially the thesaurus kind, have many similarities to indexes when it comes to looking up a topic. Taxonomies, especially the hierarchical kind, are also similar to a table of contents or the navigation aid to a set of content.

Despite the apparent similarities in hierarchical structure and the the purpose of supporting browse navigation, the differences between a table of contents and a hierarchical taxonomy, however, are far greater than the differences between a displayed index and a search-supporting thesaurus.

A table of contents provides navigation, whether for a printed book or large document or for an electronic document or collection. In fact, in a MS Word document with headings, a table of contents that is generated in the left margin pane from those headings is called “Navigation.” Labels in a table of contents or navigation system are arranged like a taxonomy but are not exactly a kind of taxonomy.

Navigation is not a taxonomy

 

Navigation or a table of contents has to perfectly reflect the content that it belongs to. It is completely customized. Two books on the same subject cannot have the same table of contents.  The same taxonomy, however, may be used for more than one content source and typically is. In a table of contents or navigation, each navigation entry, menu label, or heading matches one-to-one to a single, specific section or web page.  Terms in a taxonomy are intended to be used more than once, so each term in a taxonomy is linked to multiple documents or content items.  As such, taxonomy terms need to be somewhat generic, whereas labels or headings in a table of contents or navigation can be specific. Taxonomy terms also need to be created with the anticipation of serving not only current content but also future content, whereas navigation or table of contents entries need only reflect the current content.

Different label wording 

In addition to being more generic, taxonomy terms differ from table of contents entries or navigation labels in other ways.

• The names of chapters and headings may be longer descriptions (such as “Procedures to Enhance the Accuracy and Integrity of Information Furnished”), whereas taxonomy terms should be concise to aid skimming. A complex topic with a complex heading, can be covered with a combination of taxonomy terms instead of a single complex term, because taxonomy terms do not need to match all content one-to-one (such as the combination of terms: Information accuracy, Information integrity, and Information-gathering procedures).

• The names of chapters and headings might be question phrases (such as “Why study statistics?”), whereas taxonomy terms should be nouns or adjective-noun phrases and start off with a “keyword” likely to be looked up (not “Why”) to support alphabetical lookup options. Even in a hierarchical taxonomy display, a list of terms at the same hierarchical level tend to be arranged alphabetically.

• Table of contents entries may be context-specific based on the parent/broader level (such as “Identification and General Terms” or “Special Concerns”), and, in fact, the same sub-heading could repeat under different broader headings. In a taxonomy, each term should be independently unambiguous.

• Table of contents often start off naming introductory information (such as “Introduction to Identity Theft”) or have sections for Conclusions, neither of which should be terms in a taxonomy. If the same topic is covered three times, in an introduction, body, and conclusions, it will be indexed with the same single taxonomy term, and the end-user will retrieve all indexed results on that topic grouped together.

• Table of contents or navigation headings can be like titles, which may be “catchy” or enticing to the reader, especially at the top level. Taxonomy terms, by contrast, are clear, concise, and common (based on what most users would call the concept), and not especially creative.

Different structure

 

Tables of contents and taxonomies also differ in their structure. Tables of contents or navigation schemes reflect the organization of content, which may be chronological, pedagogical, from fundamental to detailed, from most important to least important, or the order of perceived user interest. In a taxonomy, the terms at each hierarchical level are arranged alphabetically by default. In a navigation there are no “related terms”, so what appear as subtopics might not be taxonomical narrower terms, but just related terms. Taxonomies, on the other hand, must follow the ANSI/NISO Z39.19 guidelines or ISO 25964 with respect to structuring hierarchical relationships: narrower terms bust be specific types, instances, or integral parts of their broader terms.  By having this standard format, a taxonomy provides organizational predictability for all kinds of users and all kinds of content.

There are certain editorial conventions for content, such as having units of a roughly standard length, which then impact the table of contents or navigation. While there are some variations, one chapter or section is typically not twice as long as another. To achieve balance, a large topic may be spread out over two or more sections, whereas several small topics are grouped together under a heading that is a serial list (such as “Poverty, Inequality, and Mobility”), or under “Other.” Thus, a table of contents topics are based on the amount of material presented. Taxonomy structure, on the other hand, looks at the terms/concepts only, and does not take into consideration the amount of content per term. There is once concept per term, not a list. Rare occurrences of two concepts combined into a single term, such as “Author voice and tone,” are the consequence of two topics being very closely related with overlapping meaning and usage.

Conclusions

While a table of contents or navigation system is not a taxonomy, nor should it be used as a taxonomy, when a legacy print source is converted to units of digital content, a table of contents is still an excellent source for creating a taxonomy.