Creating Class Hierarchy by Factoring Attributes
The Teacher View and the Employee View can be used as hints for creating intermediate classes above the leaf classes. Inspection of these views will provide ways for factoring attributes up higher in the class hierarchy. The term factoring attributes up refers to moving the definition of the attributes up as high as possible in the class hierarchy. Looking at the multi-type views will likely show you which attributes can be factored up and what name you should assign to the new intermediate classes above the leaf nodes. The name is usually the same name as the multi-type view that you are using.
To create the intermediate classes above the leaf classes, simply add the Teacher and Support Classes above the tentative classes and factor up the common attribute based on the multi-type view. The result is shown below.
Next: Adding the Student Class to the hierarchy. Also see the related content below.
More on the general topic: Multi-Type Views
- Teacher View
- Employee View
- Adding the Student Class to the Hierarchy
- Adding the Person Class to the Hierarchy
- Object Schema for Relational Schema