This unit delves deeper into database concepts introduced in the previous unit. It describes requirements of a database for spatial data including data security concerns, ability to support concurrent users, security against data loss, and prevention of unauthorized use.

This final unit in the spatial databases module looks at the complex issue of relationships and how they can be coded. The important concept of planar enforcement, introduced here, is referred to several times in later units.

This unit outlines fundamental concepts in database systems and their integration with GIS, including advantages of a database approach, views of a database, database management systems (DBMS), and alternative database models. Three models—hierarchical, network and relational—are discussed in greater detail.