Developing a Conceptual Model › Identifying Relations › Step 1: Identifying Relations Between Entities

Step 1: Identifying Relations Between Entities

This step details relation cardinality, which is the number of entity instances for a relationship. This topic contains examples that illustrate different types of data relationships.

Use these examples as guidelines to identify your entity-to-entity connections and draw an ERD for your data model. Let us examine two separate entities in your model, Customer and Order, and find out what the significant connection between them is.

You can tell that a relationship exists between these two entities because the customer places the order and the order is placed by the customer, as illustrated in the following example of a common ERD.

This relationship is viewed from both perspectives: from a customer and from the order. Viewing a relationship from more than one perspective is important because this gives you more information about the nature of the relationship.

With CA 2E relations, the implementation of the data model is one-way, except for the Extended by relation.