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Introduction
What is a database?
What's in a database?
The Internet
Library Catalogs
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Online Databases
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What Is a Database?

The IBM Dictionary of Computing defines a database as:

"A collection of data with a given structure for accepting, storing, and providing, on demand, data for multiple users."

Databases run on computers. Each database is set up according to the needs of its creator. Many companies design databases to store their financial and research data. U.S. government agencies create very large databases to hold information. Although there are many different types of databases used for a variety of purposes, in this tutorial we will focus on three specific types of databases:

1. Online library catalogs
2. Electronic periodical indexes
3. Internet search engines

Types of databases

1. Online library catalogs

   The Online Library Catalog replaces the old card catalog found in most libraries in this country throughout the 20th century. Like the card catalog the new online catalog assists library patrons in locating books and material owned by the library. Unlike the old card catalog, the online catalog may also provide library patrons with access to numerous other library collections. The newest online catalogs even catalog and provide library patrons access to World Wide Web sites on the Internet.

   Card catalogs allowed library patrons to search for books by author's last name, the exact title of the book, or by Library of Congress Subject Headings. In addition to these three categories, most online catalogs allow library patrons to search for information using keywords from the title, and keywords from the LC Subject Headings rather than the exact subject heading. Many online catalogs also allow library patrons to search for information in the "notes field" of the catalog record, which can include the "Table of Contents" of the book. The searching capabilities of the online catalog are a great improvement from the old card catalog.

2. Electronic periodical indexes

   Electronic periodical indexes provide library patrons access to individual magazine article citations. With this citation information the library patron can locate the print version of the article. Some electronic periodical indexes also provide library patrons access to the full-text of individual magazine articles. The searching capabilities of electronic periodical indexes is an improvement upon those of the print periodical indexes in that they allow library patrons to search by keywords as well as allowing patrons to combine numerous subject headings in one search. One downside of electronic periodical indexes is that they don't allow the library patron to browse through the index. This browsing feature can be very helpful when a person is trying to locate information on a topic unfamiliar to them.

3. Internet search engines

   Internet search engines are basically electronic indexes of information found on the Internet. We will be focusing on search engines that index World Wide Web pages. Unlike online library catalogs and electronic periodical indexes, most Web search engines are not constructed by human beings. Online library catalogs are created by catalogers who follow guidelines and rules to describe a book and assign subject headings. Electronic periodical indexes are created by indexers who also use guidelines to index magazine articles. These indexers also write an abstract which summarizes what the article is about and is searchable by keyword. Most Web search engines are created automatically by computer programs.

   Some of the largest and most popular Web search engines are constructed when the Web search engine sends out a command to search all Web sites and make copies of the individual Web pages. The copied Web pages are sent back to the Web search engine which uses another computer program to organize the copied Web pages. Search engine indexing programs use various techniques to organize Web page information including:

• Counting the number of times a word is used on a Web page
• Attempting to determine the context in which words are used
• Ranking words in order of perceived importance

Because Web search engines rely on computer programs to do the indexing, search engines have unique limitations. No matter how "good" the search engine indexing software is, it cannot perform a crucial function essential to all good indexing--it cannot think. An essential factor in good indexing involves the indexer's ability to think and to interpret meaning. Because computers cannot think they are not able to make decisions concerning what a Web site is about. Interpretation is a very complex process and is well beyond the abilities of a computer. As a result of this inherent limitation on the part of computers, Web search engines often provide meaningless responses to a searcher's inquiry.