The diagram in Figure 4-1 shows the parts of the database we'll use in this example. The diagram might not represent the final version, but it reflects pretty well what we know at this point.
Figure 4-1. A part of the database that our sample application is concerned with.
The four tables in Figure 4-1 have the following purposes:
The term neighborhood is sometimes used to refer to a set of tables such as the one in Figure 4-1. You select the main table (or main tables) needed by a certain business process or use case. Then you look at each one of the neighbors of each main table to see whether you should take that neighbor into consideration when designing a procedure to support that use case. Sometimes you even need to use the neighbors of the neighbors to get the complete picture. It's always a good idea to set up a neighborhood for each use case in an application.
Let's take a look at the eight rules that govern the sample application and decide how to implement each one of them.