A relationship is an association between primary or foreign key attributes of one or more logical data objects.
You can define the following types of relationship between attributes:
Identifying
A relationship between two attributes where an attribute is identified through its association with another attribute.
For example, the relationship between the Branch_ID attribute of the logical data object Branch and the Branch_Location attribute of the logical data object Customer is identifying. This is because a branch ID is unique to a branch location.
Non-Identifying
A relationship between two attributes that identifies an attribute independently of the other attribute.
For example, the relationship between the Account_Type attribute of the Account logical data object and the Account_Number attribute of the Customer logical data object is non-identifying. This is because you can identify an account type without having to associate it with an account number.
When you define relationships, the logical data object model indicates an identifying relationship as a solid line between attributes. It indicates a non-identifying relationship as a dotted line between attributes.