What role does the entity-relationship (ER) diagram play in the design process?

Answer 1

A completed ER diagram is the actual blueprint of the database. Its composition must reflect an organization's operations accurately if the database is to meet that organization's data requirements. It forms the basis for a final check on whether the included entities are appropriate and sufficient, on the attributes found within those entities, and on the relationships between those entities. It is also used as a final crosscheck against the proposed data dictionary entries. The completed ER diagram also lets the designer communicate more precisely with those who commissioned the database design. Finally, the completed ER diagram serves as the implementation guide to those who create the actual database. In short, the ER diagram is as important to the database designer as a blueprint is to the architect and builder.