Supplemental Navigation Systems
Two Out of Three Ain't Bad

Supplemental navigation systems, also called remote navigation elements, give users additional, non-hierarchical ways to navigate a site. Three common supplemental navigation systems are tables of contents, indices, and site maps. How can you choose?

Rosenfeld and Morville explain why some supplemental navigation systems are better than others.

Tables of contents

Tables of contents are effective supplemental navigation systems because users recognize them from books. They work best for large sites organized hierarchically.

A good table of contents should show at least the top two levels of the site's hierarchy, preferably in a format that visually reinforces that hierarchy. Users can sidestep the hierarchy, however, by using the table of contents to navigate to any level of the site.

The best part about tables of contents is that they're easy to implement as long as you've got a solid hierarchy already. Just take titles from the first few levels of your site, arrange them in the right order, and you've got a table of contents.

Indices

Site indices are detailed, alphabetical lists of terms that have more entries and less levels of hierarchy than tables of contents. Indices, like search engines, help users who know exactly what they're looking for. And, like tables of contents, they work because users have seen them before.

Lou Rosenfeld's Web Architect article Organizing Your Site from A to Z suggests four steps for creating a site index:

• Remind yourself what your users are like and what information they will want to find at your site.

• Make a list of your site's important content components, defined as "groups of pages in your site, individual pages, or sections of an individual page." Be thorough. Look at every page of your site to make sure you don't miss anything big.

• Trim your index by grouping entries together. That is, don't give "Staff Biographies" and "Staff Email Addresses" separate entries if both pieces of information are on the same page. Say "Staff."

• Consider term rotation, for instance, Rosenfeld's example of adding "Map, New Orleans" to an index that already lists "New Orleans Map."

Site Maps

A site map graphically illustrates a Web site's architecture. They're great in theory, but Peter Morville points out that they usually don't work in practice. To help ward off pointless site maps, he's invoked three Cartography Commandments.

• "Thou shalt not use bubble gum." Using a site map in place of good architecture is like holding a jet together with gum. 'Nuff said?

• "Consider a table of contents." Like we've said, tables of contents are easy and effective.

• "Maps should be symbolic." Site maps are a metaphor, not a direct translation.
  If you try to literally represent every page as a graphic, you're in trouble. Think conceptual, not concrete.

We can infer that Morville's fourth commandment might be "Thou shalt avoid automatically generated site maps." They wreak havoc on usability, they don't work unless a site is strictly hierarchical (few are), and are often poorly maintained. When it comes to supplemental navigation systems, you might as well stick with a table of contents or an index.