User's Guide and Reference

The purpose of DB2 Spatial Extender

You use DB2 Spatial Extender to create a geographic information system (GIS): a complex of objects, data, and applications that allows you to generate and analyze spatial information about geographic features. Geographic features include the objects that comprise the earth's surface and the objects that occupy it. They make up both the natural environment (examples are rivers, forests, hills, and deserts) and the cultural environment (cities, residences, office buildings, landmarks, and so on).

Spatial information includes facts such as:

• The location of geographic features with respect to their surroundings (for example, points within a city where hospitals and clinics are located, or the proximity of the city's residences to local earthquake zones)
• Ways in which geographic features are related to each other (for example, information that a certain river system is enclosed within a specific region, or that certain bridges in that region cross over the river system's tributaries)
• Measurements that apply to one or more geographic features (for example, the distance between an office building and its lot line, or the length of a bird preserve's perimeter)

Spatial information, either by itself or in combination with traditional relational database management system (RDBMS) output, can help you to design projects and make business and policy decisions. For example, suppose that the manager of a county welfare district needs to verify which welfare applicants and recipients actually live within the area that the district services. DB2 Spatial Extender can derive this information from the serviced area's location and from the addresses of the applicants and recipients.

Or suppose that the owner of a restaurant chain wants to do business in nearby cities. To determine where to open new restaurants, the owner needs answers to such questions as: Where in these cities are concentrations of clientele who typically frequent my restaurants? Where are the major highways? Where is the crime rate lowest? Where are the competition's restaurants located? DB2 Spatial Extender can produce spatial information in visual displays to answer these questions, and the underlying RDBMS can generate labels and text to explain the displays.

Several other examples of the uses of DB2 Spatial Extender appear in this book, especially in Retrieving and analyzing spatial information, Writing applications for DB2 Spatial Extender, and Spatial functions for SQL queries.