Subject Directories of the Internet Subject Directories of the Internet Subject directories, also known as subject trees or hierarchies, can be extremely useful when conducting Internet research on a specific topic. Subject directories rely upon an organizational scheme such as a controlled hierarchy of often unique subject headings, similar to that used for subject indexes for books in libraries. As a consequence of the indexing process, most resources found in subject directories may not be as current as those found using a keyword search engine . Many subject directories provide a keyword or phrase search engine that will search either the subject headings or some aspect of the linked resource. A2Z , from Lycos.
Sites seem to be selected primarily on popularity as measured by traffic volume.
There are 16 major headings and 48 minor headings which allow the first time user to locate relevant information rapidly. Most guides are intentionally narrow in focus. Some guides were created by graduate students at the University of Michigan's School of Information, others by faculty and graduate students at other institutions. Encyclopedia Britannica's Internet Guide Directory service that classifies, rates, and reviews more than 125,000 Websites. Emphasizes quality sites.