Taxonomy Design Research

I recently wrote an article “Taxonomies: Connecting Users to Content” for an online publication, Boxes and Arrows, on information architecture (IA) and user experience (UX). As I was working with the editors on the section of gathering information from users, I realized that IA and UX have very formalized researcher roles. There is a job title for “UX Researcher” with career guides and resources on what skills are needed, and many more jobs on job board sites posted for “UX researcher” than for “taxonomist.” Meanwhile, there is no such job as a “taxonomy researcher.” But designing and developing taxonomies, which are often part of information architecture or UX, does require research, including user research.

Taxonomy research is not as formalized and does not involve standard tools, as UX research does, but it is still important. There is not nearly as much published about taxonomy research as there is for UX research. However, certain research practices, I have found, are common in the taxonomy consulting industry. It’s a matter of best practices. Even when taxonomies are designed internally and not with an external taxonomy consultant’s assistance, research is still part of the process. The type of research may vary based on the background and experience of the person leading the effort.

Taxonomy design research includes:

• Interviewing sample users and other stakeholders
• Gathering input from brainstorming sessions
• Analyzing content to be tagged
• Analyzing existing vocabularies of all kinds
• Analyzing any search log reports
• Taxonomy testing

While UX research is a form of user research, taxonomy research involves both user research and content research (or content analysis), because a taxonomy needs to consider both user needs and content suitability.

Interviewing stakeholders

The primary method of gaining user input on a taxonomy is through interviews and questionnaires, ideally both in combination, where a conversation follows up on a list of questions sent to the person being interviewed. It’s important to ask different kinds of questions tailored to the different kinds of users, questions dealing with tagging vs. questions dealing with retrieval of content. The input gathered from users in these interviews and questionnaires can be used to better design and the taxonomy and its user interface, to obtain use cases to later test the taxonomy, to identify possible facets for a faceted taxonomy, and also to collect some concepts for the taxonomy.

Brainstorming sessions

Another method of obtaining input from users is through a brainstorming session. This method is particularly useful for internal enterprise taxonomies. Representative users from different departments can contribute their ideas by suggesting sample terms, which are written down on a white board, flipchart, or sticky notes, and then working with a facilitator, the brainstorming group can remove outliers, bring together synonyms and similar terms, and come up with categories or facets to group the terms. PoolParty is the only taxonomy management software that has an integrated brainstorming module called CardSorting.

Analyzing content

After determining the scope of content inclusion, content analysis should be performed on a representative sample of content of each of the different types and subject areas of content that will be tagged and retrieved, to identify topics and named entities relevant to the content. This form of content analysis is similar to indexing without a controlled vocabulary.  The taxonomist assumes the role of an indexer or someone tagging the content and notes what index terms or tags would best describe the content.

Automatic term extraction involves using text analytics software (which may be incorporated into taxonomy management software, such as in PoolParty) to extract candidate taxonomy terms based on their frequency and relevancy within a body (corpus) of text content. The suggested terms need to be analyzed for the context of their usage before determining whether they should be added to the taxonomy.  

Analyzing existing vocabularies

If an organization already has some controlled vocabularies (taxonomies, thesauri, term lists, terminologies, glossaries, etc.), whether currently in use or not, these should be analyzed as sources of terms for incorporation into the new taxonomy. Assuming the project is to create a new taxonomy, any existing controlled vocabularies may have been for a different purpose, so only some of the terms would be relevant. Glossaries tend to have too many detailed terms that are not needed for information retrieval, but these and any other vocabularies are good sources for synonyms/alternative labels.

Analyzing any search log reports

When creating or editing a taxonomy, it’s always useful to look at search logs, which indicate what users have been typing into the search box. Search log reports can be sorted by search string frequency, so that the most frequently used search strings are considered for inclusion into the taxonomy. The search strings should be edited to confirm with taxonomy style and policy, but the exact search strings should be included as synonyms/alternative labels to support future searches.

Taxonomy testing

Near the completion of a taxonomy project, there should be some activity of taxonomy testing. Taxonomy use testing should test a taxonomy’s suitability for tagging content by manually test-tagging sample documents and determining if the desired terms are available in the taxonomy. Taxonomy use testing should also test the retrieval capabilities of the taxonomy. This is done by attempting to retrieve pre-identified documents with searches conducted by sample users with the search terms of their choice.

Other test on taxonomies, such as card sorting and A-B testing, which are also used in UX navigation testing, may be used in taxonomy development to test the preferences of the top two levels of a hierarchical taxonomy, but such tests are less suitable for multiple-level hierarchical taxonomies or for faceted taxonomies. More details are in my previous blog post on Testing Taxonomies.

Conclusions

Creating a taxonomy involves many research-related tasks, which can take up as much time or more than actually creating terms in a taxonomy. While there is a creative aspect to developing a taxonomy, a taxonomy also has to be based on research and analysis, with the emphasis on analysis. The research is more qualitative than quantitative, though.

Taxonomies for Filtering and Sorting

Taxonomies are versatile and may be used for various purposes. Originally designed to support hierarchical browsing of topics linked to content, they also may be implemented to support more accuracy in searching. Most discussions of taxonomies have focused on browse and/or search, but taxonomies may function in additional ways: enhancing filtering and sorting.

Filtering

Taxonomies structured into facets serve a combination of search and browse, and thus serve what is often called “faceted search” or “faceted browse” (as described in a previous blog post, Faceted Search vs. Faceted Browse). However, it’s simpler, more accurate, and more helpful in understanding facets to consider a faceted taxonomy as serving a distinct role from browsing or searching, that of filtering.

Filtering is a common function which is not limited to use with taxonomies. Filtering can be done by non-taxonomy attributes, such as keyword, author, date, etc., if these are set up as metadata and implemented as filters. We see filters in situations which lack taxonomies in options in the email inbox or lists of documents in file management user interfaces. We also find filters on documents in SharePoint libraries and other content/document management systems, which may include taxonomies. In a user interface, the icon for filtering is a funnel (where you can imagine that it is lined with a cone-shaped filter paper).

Filters may be known by other names, such as “Refinements”/“Refine by” or “Limit by.” These designations may be used interchangeably, although they tend to be used different circumstances. “Filtering” may be done on search results or on a complete set of records, such as a list in a spreadsheet or table. “Refining” or “limiting,” on the other hand, would usually be performed only on the results of an executed search, as a further refinement or limiting factor on an initial set of search results which turned out too large. “Refining,” furthermore, suggests a more careful search process, so this name is more often used in research databases or other repositories of articles and resources.

A relatively small faceted taxonomy comprising short lists of terms for each facet/filter, from which the user can select from a displayed list or drop-down, is both easy to use and, with proper tagging, can achieve accurate retrieval results.

 

Sorting

Sorting is done on content in a spreadsheet or table, where data on content items is in different columns, with sorting done by an attribute of an individually selected column. Sorting could be by numeric order, by alphabetic order, by date, or by the mere presence of a binary value.  Indeed, most sorting does not involve taxonomies, but it can.  If a column is for “Topic” and items have been tagged with taxonomy terms, then the items can be sorted by taxonomy term topic.

The function of sorting with taxonomy terms may not be quite as common as filtering, since it is not done on search results but only on data in a table or spreadsheet. However, in many situations content items are presented this way: content in spreadsheets and databases, messages in an email inbox, content items in SharePoint libraries and various kinds of content management systems, and many other applications. Furthermore, it’s often simpler to sort than to filter.

Sorting is nevertheless a function associated with taxonomies, at least in the definition of taxonomy in the ISO standard for controlled vocabularies. ISO 25964-2:2013 in section 3.83 defines taxonomy as a “scheme of categories (3.5) and subcategories that can be used to sort and otherwise organize items of knowledge or information.”

The following screenshot from SharePoint shows the availability of both sorting (by clicking on the down-arrow next to a column name, such as Topic), and filtering (by selecting Topics in the filter pane on the right).

Summary

As taxonomies are versatile, the same taxonomy can be used for multiple purposes: browsing, searching, filtering, and sorting. However, a taxonomy design usually can be optimized for the user experience of only one or two implementations. So, a taxonomy that delivers a great user experience for hierarchical browsing, might not be best suited for filtering or sorting, or vice versa. Filtering is more accommodating for various taxonomies than is sorting, since it may not be necessary to display the entire taxonomy in filters.

Trends in Hierarchical Taxonomy Displays

Taxonomies connect users to content. So, how a taxonomy is displayed to users is very important in its effectiveness. This is a topic about which I gave a conference presentation back in 2011 and will present again next week. As I update my previous presentation, looking at some of the same public websites with taxonomies, I have observed some changes that might be considered as trends.

While faceted taxonomies (used to filter/refine/limit results by certain criteria with choices of taxonomy terms) have become more common on ecommerce or other database websites, they are not suitable in all circumstances, and when a taxonomy has a large number of topical terms, a hierarchical arrangement of those topics might be better.

Displayed full hierarchical taxonomies, however are more difficult to find. They are not as often the default.  Some have disappeared entirely such as the Yahoo directory, which was discontinued in December 2014 after 20 years. (Admittedly, trying to classify as many websites as possible into a hierarchy, as the web keeps growing, is a never ending task.) In other cases, the search box is more prominent on the page, and the link browse categories needs to be hunted for.

In the past, I had observed two main different kinds of hierarchical displays: one-level-per-page and expandable hierarchies with plus signs. The first has evolved, the second is has become rare, and a third method has emerged.

One level of taxonomy hierarchy per page was the design of the former Yahoo directory and had been early on the style followed on other sites. An example that closely follows the Yahoo Directory, is the dmoz/Open Directory Project. A list of category labels or topics at each level takes up the entire screen/page display, without the display of other content. Displaying additional content on every page has become important, so hierarchical taxonomy categories now tend to be confined to more compact lists to free up space on the web page for content. This works for some taxonomies, not all. Meanwhile, a list of terms at the same level that take up the entire page is a style that is rarely followed anymore.

Expandable hierarchy “trees,” typically with plus signs next to topics to expand a topic’s subcategories has become quite rare, at least in public web sites. An example are the USA Today topics. This hierarchical taxonomy design had been developed based on the recognizable desktop file folder structure, such as in Windows. In the meantime, users have become familiar with different representations of topic hierarchies on the web, so mimicking expandable file menus is no longer the only way to engage users. Expandable topic hierarchies are not as easy to update and change on websites and, it can take a long time to load the web page. Expandable hierarchies allow the users to have more than one hierarchical level expanded at once, which facilitates exploring the taxonomy. As much as we taxonomists might enjoy browsing a taxonomy, the goal is to get users to content rather than have them spend time exploring the taxonomy.

A third method of displaying multiple levels of a hierarchical taxonomy is through “fly-out” subcategory lists. Examples include Lynda.com (under "Browse the Library") and Books & Authors. I had not noticed this method before, so it seems to be a new trend. They are similar to submenus in website navigation, but rather than for website navigation, the topics are linked to indexed content items, which are listed in a result set for each subtopic. Fly-out subcategories allow the users to still see the parent category list, if the user wanted to back out to it, like in an expandable tree hierarchy. But unlike an expandable tree hierarchy, you cannot have multiple parent categories expanded at the same time, which is not that important anyway. The fly-out subcategory style is thus a positive trend in hierarchical taxonomy displays.

Information Architecture and Taxonomies

While interest in “information architecture” by that name has declined in the past decade, interest in what information architecture involves continues to be strong, and perhaps there is some merging of the fields of taxonomy and information architecture.

At one point in my career I wanted to be an information architect, to organize the pages and menus of websites and intranets.  The discipline’s leading professional association, the IA Institute additionally describes the field as “The structural design of shared information environments.” But within a couple of years, I found that interest in my information architecture skills, at least for small websites (“little IA”) was getting squeezed out for skills in either graphic design or technical web development. Over time it also seemed as if information architecture was being replaced by the growing field of user experience design (UXD). Indeed Google search trends show a definite decline in interest in the phrase “information architecture” during the same period of a steady growth in interest in “user experience.”

I was therefore pleasantly surprised to find that information architecture was one of the themes at this year’s Taxonomy Boot Camp (Washington, DC, November 5-6, 2013), the leading conference dedicated to taxonomies.

Information architecture was a central part of the keynote “Taxonomy Is Power: Bringing It All Together,” presented by Bob Boiko. He started off explaining that information systems are a triad of people, information, and technology. But he, too, had observed that information architecture (IA) has often been “captured” by user experience (UX), moving away from technology toward the user, but the “information” piece of the triad sometimes gets lost along the way and needs more attention. Bob defined information architecture as “the art and science of designing information structures” and that information architects live in the space between art (design) and science (technology). Information architecture is also about naming things, and taxonomies can help engineers and designers name things for both the front end and back end of an information system. Bob said that taxonomists should look at and “own” the concept of information architecture.

The conference also featured a session of three presentations under the heading “User Experience (UX) in Taxonomy Design.” Michael Rudy, of  the consultancy Factor, spoke on the benefits of integrating user experience  with information management, and Bram Wessel, also of Factor, presented on how different methods of user research, common in user experience design, such as card sorting, tree testing, personas, and prototyping, are also applicable to taxonomies. Taking a different angle to the issue, Ben Licciardi of PPC presented methods of designing the manual indexing/tagging interface for taxonomy use.

There are various perspectives and approaches to this field, whether stressing structure as in “architecture,” naming, as in “taxonomy,” or meaning, as in “semantics.” Different labels may resonate better with different audiences. The week of the conference I was also indexing a book on user experience design (a small project to do on the plane and to broaden my knowledge of the subject). While “taxonomy” was not mentioned in this light book, “semantic design” was the name of a section which mentioned information architecture, organizing information, and metadata.

Several years ago, perhaps 2007, when I introduced myself as a taxonomist to someone at a professional conference, I was asked what the difference was between taxonomists and information architects. My answer then is the same as it is now: there is definitely a significant area of overlap between the skills, tasks, and responsibilities in both professions, although there are some areas that concern information architects and not most taxonomists, and there are areas that concern taxonomists and not most information architects. So, it may only depend on what kind of information architect or kind of taxonomist you are. I hope one day to also attend the main information architecture conference, the IA Summit and continue this discussion, as interest in taxonomies is remaining strong.