Dealing with hierarchies

SAP Design Guild’s series on hierarchies has a lot of good information on the design of interface hierarchies, how users perceive them, and how to effectively use them in your software or Web site design.

Hierarchies in the "real" world tend to be shallow and simple, like the table of contents in a book or the organization of a file cabinet. In software interfaces, hierarchies tend to be deeper and more complex with many more items and levels. It is easier for people to get lost within these systems because it is similar to navigating a maze. "People need to know where they are, why they are there, where they came from, and where they can go."

It is easier for people to understand a hierarchical system if they can see their choices. "[Pulldown] menus should contain fewer items because they are arranged vertically and without internal structure, are only temporarily visible and - in the case of cascading menus - require some advanced mouse skills from the users, which distract their attention."