According to Rosenfeld and Morville, organizational systems are composed of organizational schemes (the shared characteristics of content items--the white pages of a telephone book uses an alphabetical organization scheme) and organizational structures (the relationship between content items--the hierarchy of a
web site).

Exact organizational schemes divide information into well defined, non-overlapping sections. This exact method of organizing information, however, presents a problem--users must know exactly what they are looking for--called "known-item" searching. For instance, one cannot search for a doctor in the white pages; instead, one must know the exact name of the doctor.

A solution to the problem of exactness is ambiguous organization schemes, which divide information into categories that lack a specific definition. Ambiguous organizational schemes are useful because people often do not know what they are looking for, do not know the correct name/label, or do not have enough information. An ambiguous organization scheme requires someone to intelligently group related items together, but these items can be grouped in a variety of ways.

One way to group items is by topic. The yellow pages of the phone book are organized by topic, and most web sites use some form of topical organization. Corporate web sites, for instance, use topical organization when presenting their products and services. (4.3)