Using Polymorphic View Objects
When you create an inheritance hierarchy of entity objects, you may want to work with rows for the subtypes and supertype at once, working with all the attributes that they share. This requires a VO with polymorphic entity usage.
If you want to create a VO to work with a specific subtype, such as Customers, you need a VO with polymorphic view rows.
These concepts are explained in detail in the subsequent slides with the simple example of the entity hierarchy, which consists of Persons, Employees, and Customers.