Overview of the Entity-Relationship Data Model

More than one formal method for data modeling exists. Most methods force you to be thorough and precise. If you know a method, by all means use it.

This chapter presents a summary of the entity-relationship (E-R) data model. The E-R data-modeling method follows these steps:

1. Identify and define the principal data objects (entities, relationships, and attributes).
2. Diagram the data objects using the E-R approach.
3. Translate the E-R data objects into relational constructs.
4. Resolve the logical data model.
5. Normalize the logical data model.

Steps 1 through 5 are discussed in this chapter. Implementing a Relational Data Model discusses the final step of converting your logical data model to a physical schema.

The end product of data modeling is a fully-defined database design encoded in a diagram similar to Figure 21, which shows the final set of tables for a personal telephone directory. The personal telephone directory is an example developed in this chapter. It is used rather than the demonstration database because it is small enough to be developed completely in one chapter but large enough to show the entire method.