The Importance of Hierarchy

Louis Rosenfeld and Peter Morville say it best in Information Architecture for the World Wide Web:

"The foundation of almost all good information architectures is a well-designed hierarchy."

Why? People understand hierarchies and have used them forever in family trees, scientific classification, language, and more. It's comfortable to start at the top, at the most general level, and move down the line toward more and more specific information. If you have a large site, you can't afford to ignore hierarchy.

The hierarchy is your primary navigation system, but it can't be the only one. You'll need other ways to navigate your site, but your hierarchy will make it easier to build them.

Your global navigation system can be based on the major categories on the top level of your hierarchy. You can translate your hierarchy into a table of contents. No matter what navigation systems you build, you'll need the solid foundation of the hierarchy to do it well.

Designing Your Site's Hierarchy

Rosenfeld and Morville have several guidelines for designing information hierarchies on the Web:

• Hierarchical categories should be mutually exclusive. This isn't a hard-and-fast rule, so feel free to put certain content in more than one category. Don't overdo the cross-referencing, or your hierarchy will get muddled.

• Consider breadth and depth (the number of options at each level of hierarchy and the number of levels in the hierarchy, respectively). Don't make your users click through lots of levels to get where they want (too much depth), and don't overwhelm them with too many options on each page (too little depth). More than 10 options on the main menu is overkill (too much breadth).

• Don't be dogmatic about the hierarchical model. If some of your content lends itself to a database, don't put into a hierarchy instead just because hierarchy is important.