Databases may sometimes be accessed through the Internet, but their contents are typically not retrieved by search engine services like Google or Yahoo! Most are available through separate Web sites that charge a fee for use, normally paid by libraries on behalf of their users. But Google or Yahoo! (and many other Internet search utilities) create databases of Web sites and organize them into directories by subject.

Every database contains only certain types and amounts of information, a characteristic called coverage. This information can typically be found in the database itself under links such as "About [name of database]," "Database information," "Title list," or "Sources," etc. Web-based databases are typically accessed from a link that is annotated with some information about coverage. Databases published in paper form normally locate this information in the front of each volume or in an introduction.

Consider the following elements of database coverage:

• What kinds of documents? Journals, magazines, books, book chapters, dissertations, audio files, statistical tables, images, Web pages, software applications

• Which disciplines? Sociology, music, chemistry, all, none?

• What time periods? The current year? 1960-1998? How often is the database updated? Hourly, daily, weekly, monthly, annually?
• What language? English only? Other languages?
• What publication types? Scholarly? Popular? Trade? All three? Others?
• What is included in the record? A whole article or chapter (full-text) or just a brief description (bibliographic citation and abstract)? Publisher and title?