User experience architecture

September 18, 2008

Five heuristics for designing classification

Whether you’re designing a home page, a store layout or a document library, you’re practicing information architecture to define a classification scheme. At the heart of this scheme is a set of classes. These act as “shelves” on which you group sets of “books” that have something in common.

For example, the classes “Red, white and rosé” classify wines by colour. “Acoustic, solid electric, semi-acoustic and electro-acoustic” categorize guitars by body style. “Starters, entrées and desserts” classify recipes by course. The wine lover knows to look in “White” for Chablis and Frascati. A guitarist confidently goes to “solid electric” to find a Stratocaster. A chef will expect to find a Pavlova under “desserts”.

An effective scheme reliably lumps similar items together and splits different items apart. Here are 5 heuristics that should help. In each example, misfit classes are highlighted.

Homogenous The classes describe similar types of things at the same level. Labels use consistent formats and labels. apples, pears, bananas, sprouts , peaches, Cox’s Pippins, apricots, actinidia deliciosa

Sprouts are out of place in the fruit bowl. Pippins are a type of apple, not a type of fruit. Actinidia deliciosa is Kiwi fruit. Although the class fits well, the latin label is inconsistent.

Mutually exclusive The classes do not overlap. Any item clearly fits in one – and only one – class. saloons, hatchbacks, coupés, family, estates, sports, 4X4s, vehicles

The two lifestyle classes, “family” and “sports”, overlap with the body style classes. “Vehicles” is a superclass of all other classes – and overlaps everything.

Collectively exhaustive As a set, classes cover all items. French, German, Spanish, Californian, Chilean

Where’s the Valpolicella?

Understandable Classes have labels that make sense to the reader. rhinovirus, tussis, cephalalgia

Coughs, colds and headaches – if you happen to be a doctor or a classicist.

Useful The classes group items in a way that supports the reader’s needs. Red books, blue books, green books, yellow books, grey books, black books, white books

Perfect if you want to coordinate your library with the soft furnishings. Otherwise, consistent, logical and useless.

For more on library science, I recommend Classification made simple” by Eric Hunter.


  1. Thanks Paul, this is a really nice set of heuristics. Is this your set or is it derived from Hunter?

    Comment by Rob van Tol — October 2, 2008 @ 1:56 pm

  2. Hi Rob, thanks for your feedback. Appreciate the nudge to reference this more thoroughly 😉

    “Homogenous” comes from ideas in the Polar Bear Book.

    MX and CE come from classical Aristotelian ideas of categorization. Here’s a nice diagram. He also talks about “clearly defined” which is subtly different from “understandable” and could perhaps be added to this set.

    “Understandable” and “useful” are taken from principles in usability. The former from Don Norman’s ideas about the gulf of execution and the latter from the goals of task analysis ( e.g Annett and Duncan).

    This is all a bit old school; Aristotle’s somewhat under attack from new ideas on prototype theory, facets and social tagging.

    Comment by uxarchitecture — October 2, 2008 @ 7:01 pm

  3. Thanks Paul. I just doing an evaluation of a document library IA, and this has provided very useful.

    As for Prototype Theory, if you haven’t seen it, Donna Maurer did a nice review of the implications of Lakoff (Women, Fire and Dangerous Things) in IA. See:

    Comment by Rob van Tol — October 3, 2008 @ 1:35 pm

  4. Thanks Paul, this is really helpful.

    Comment by Maarten Bressinck — August 14, 2012 @ 9:48 am

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