The highest level of abstraction for the data model is called the entity relationship
diagram (ERD). The ERD reflects data at its highest level of meaningful abstractions and
their relationship to each other. The entities of the organization are identified, as well as
the relationships between those entities.

Fig. 7.3.2 shows the symbol that identifies the entities and relationships in an ERD.

Fig. 7.3.2 The high level data model.

As an example of the ERD for a manufacturing company, the ERD might look like that
seen in Fig. 7.3.3.

Fig. 7.3.3 Some simple entities and their relationship.

The ERD is important as a high-level statement of what the data model is all about. But
—of necessity—there is very little detail found at the ERD level.

The Dis

Chapter 7.3: Data Modeling for the Structured Environment