E-Commerce Taxonomies

Happy Cyber-Monday! Coincidentally, this week, which is cyber-week for some retailers, I am giving a conference presentation, at Gilbane in Boston on November 29, on “Taxonomies for E-Commerce.”

As online shopping grows, the organization of products for sale on e-commerce websites becomes increasingly important, and there is also more standardization. Websites present the option to either search (used by customers who know what they want and what to call it), and browse (used by customers who are not sure about what they want or what to call it). For holiday gift shopping, browsing tends to be more common than usual, so displayed taxonomies take on a particularly high visibility at this time.

For browsing, e-commerce websites typically organize their products into hierarchical categories, which are then narrowed by the use of facets. Top level categories correspond to “departments” and could be as few as 2-3 for a specialty retailer or as many as 12-17 for a general/mass merchandize retailer. Usually the hierarchy extends one or two more levels deeper, although a very large retailer may find the need for an occasional fourth level.

At the lower levels of the hierarchy, the customer may then refine the set of products by use of facets (also known as attributes, filters, refinements, dimensions, “limit by,” or “narrow by”). The facets are for characteristics that cut across multiple categories. Facets may be for size, color, price range, material, brand, style, special features, and perhaps even customer rating. These facets will vary depending on the department or broader category type. The terms within a facet, known as “facet values” or “attribute values,” are usually in a flat list The user selects a value from each of multiple facets in combination. In some cases, if check boxes are provided, the user is permitted to select more than one value from within the same facet.

Typically retailers are more concerned about the selection and implementation of technology than in the design of the taxonomy. After all, a hierarchical taxonomy of products would appear simple to design, and even the facets are not too challenging to develop, especially with lots of competitor e-commerce websites to analyze and compare. However, my experience working as a taxonomy consultant on e-commerce taxonomies has led me to realize that creating and editing e-commerce taxonomies is not as easy as it seems.

My conference presentation discusses seven challenges:

1. Distinguishing a subcategory from a facet value
At the higher levels, categories are obvious. Standard facets (size, color, price range, etc.) are also obvious. But the distinction between the most specific subcategories and specialized facets can get blurred.  Can “type” be a facet? Is a “plaid shirt” a subcategory of shirts, or is plaid a value in a “pattern/type” facet? Are gas and electric stoves subcategories of stoves, or is “energy source” a facet of stoves? Factors to consider in making these decisions include user perceptions and the number of existing levels of subcategories and numbers of facets.

2. Different categorization options
There are often product categories that are difficult to classify. For example, do video games belong in “Toys and Games” or in “Electronics”? Does Home Theater belong in the “Television/Video” or the “Audio/Stereo department? Having the category in both locations, as the polyhierarchy feature of a taxonomy, is possible. But a breadcrumb trail might follow only a single path, not both, and too many polyhierarchies can be confusing to users.

3. Related items
E-commerce taxonomies are hierarchical and generally do not have associative/non-hierarchical relationships between categories. It is not needed in most cases, but accessories to products and related services (installation, repair, etc.) are clearly related to specific product categories. Taxonomic standards might have to be ignored if making such categories narrower to their main product is the only option. But other, creative display options might be possible.

4. Sort order options
Generally a long list of terms, over a dozen, is easier to scan if alphabetized, whereas a short list of under a dozen terms is better suited to some other prescribed “logical” order. Sort order inconsistency will result, however, if the number of subcategories fluctuates. Determining the “logical” order is also a challenge and often centers around what is most important or popular.

5. Competitor website comparisons
For e-commerce taxonomies (unlike enterprise taxonomies), it’s great to be able to compare with competitors. However, often a retailer is somewhat unique, and no single competitor has exactly the same product categories. Furthermore, it’s important to distinguish between category and content comparison from design comparison. Design may be an extension of a retailer’s overall unique brand graphic design.

6. Web site vs. physical store organization
Physical (“brick and mortar”) stores have their own organization for products that might not work online, but there may be pressure to mimic physical store organization to provide a consistent user experience. While it may make sense to have the biggest sellers up front or at the top of the list, product size (a factor in physical store organization), should not necessarily be a factor in online organization.

7. Business needs vs. taxonomy best practices
Online merchants might want to make certain product categories more prominent, by changing the sort order, adding polyhierarchy locations, or even moving a subcategory up a level. It’s important to keep the integrity of the taxonomy intact, though, so that it remains intuitive for the customers to use.

In sum, product taxonomies are not as simple to create as might be expected. Taxonomy design may be under constraints, and business needs can challenge taxonomy standards. Creative solutions may be needed, and customer perspectives need to be considered through creating personas and/or through user testing.

5 thoughts on “E-Commerce Taxonomies

  1. This is perfect as I'm just wrapping my head around facet taxonomy best practice.

    I do have a question regarding point #2 about cross categorization in regards to polyhierarchy. Let's say video games primary category is within 'Toys and Games' but I also list it within 'Electronics'. Would the Video Games link within 'Electronics' point to original category page /toys-games/video-games or would it be also be /electronics/video-games with a rel="canonical"? I'm assuming the former but polyhierarchy is new to me and I may completely wrong on both accounts.

    Great article and thanks for the help!


  2. How polyhierarchy is actually managed depends on the system. In some cases, there is only one actual (or as you say "original") parent category, and others point to it, but in other cases, both parent categories are treated equally. Taxonomy management software manages polyhierarchies as equally valid in all parent-child relationships, but not all content management systems do.

  3. I'll have to check if the new CMS has taxonomy management software but my initial search says otherwise.

    Thanks for the help.

  4. Hi Heather,

    Working on a taxonomy for an ecommerce site… debating adding a shirts category under mens vs listing out types of shirts independently eg. polos, tshirts, casual, etc.

    I'm not liking 18 categories under mens and womens. Adding a shirts and tops category with subcats would reduce the number to a more "scannable" list.

    Your thoughts?


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