Databases and database systems have become an essential component of everyday life in modern society. In the course of a day, most of us encounter several activities that involve some interaction with a database. For example, if we go to the bank to deposit or withdraw funds; if we make a hotel or airline reservation; if we access a computerized library catalog to search for a bibliographic item; or if we order a magazine subscription from a publisher, chances are that our activities will involve someone accessing a database. Even purchasing items from a supermarket nowadays in many cases involves an automatic update of the database that keeps the inventory of supermarket items. The above interactions are examples of what we may call traditional database applications, where most of the information that is stored and accessed is either textual or numeric. In the past few years, advances in technology have been leading to exciting new applications of database systems. Multimedia databases can now store pictures, video clips, and sound messages. Geographic information systems (GIS) can store and analyze maps, weather data, and satellite images. Data warehouses and on-line analytical processing (OLAP) systems are used in many companies to extract and analyze useful information from very large databases for decision making. Real-time and active database technology is used in controlling industrial and manufacturing processes. And database search techniques are being applied to the World Wide Web to improve the search for information that is needed by users browsing through the Internet. To understand the fundamentals of database technology, however, we must start from the basics of traditional database applications. So, in Section 1.1 of this chapter we define what a database is, and then we give definitions of other basic terms. In Section 1.2, we provide a simple UNIVERSITY database example to illustrate our discussion. Section 1.3 describes some of the main characteristics of database systems, and Section 1.4 and Section 1.5 categorize the types of personnel whose jobs involve using and interacting with database systems. Section 1.6, Section 1.7, and Section 1.8 offer a more thorough discussion of the various capabilities provided by database systems and of the implications of using the database approach. Section 1.9 summarizes the chapter. The reader who desires only a quick introduction to database systems can study Section 1.1 through Section 1.5, then skip or browse through Section 1.6, Section 1.7 and Section 1.8 and go on to Chapter

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