So far, four tentative classes have been created as shown in this diagram. The same attributes (Name, Date of birth, and Hire date) are repeated in each class. Additionally, two classes have additional attributes (Workstudy has Entry Date and Professor has Tenure Date).
Each of these tentative classes will become what is know as leaf classes in the class hierarchy. Leaf classes are at the end, or bottom, of the class hierarchy much like leaves are at the end of tree branches. The hierarchy now must be expanded to intermediate or non-leaf classes. Potential intermediate classes can be identified by either inspecting the tentative classes for shared attributes or using multi-type view as defined in the relational schema. In this example, we will use multi-type views to define new classes.
Next: Multi-type views. Also see the related content below.
More on the general topic: Using Type Codes to Construct Classes
- Support View
- Support Class
- Professor View
- Professor Class
- Instructor View
- Instructor Class
- Workstudy View
- Workstudy Class