Chapter 3 Building Conceptual and Logical Diagrams
An inheritance allows you to define an entity as a special case of a more general entity. The general, or supertype (or parent) entity contains all of the common characteristics, and the subtype (or child) entity contains only the particular characteristics.
In the example below, the Account entity represents all the bank accounts in the information system. There are two subtypes: checking accounts and savings accounts.
The inheritance symbol displays the inheritance status:
| IDEF1X | E/R and Merise | Description |
|---|---|---|
|
|
Standard |
| — | 
|
Mutually exclusive inheritance |
|
|
Complete inheritance |
| — | 
|
Mutually exclusive and complete inheritance |
Inheritances in the Barker notation
There is no separate inheritance object in the Barker notation. You represent an inheritance by placing one entity symbol on top of another. Barker inheritances are always complete and mutually exclusive. The supertype lists its subtypes on the Subtypes tab (see Entity properties).
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