ABAP Objects supports nested, or compound interfaces. A compound interface contains one or more interfaces as component interfaces. These may also contain interfaces as components, thus allowing multiple-level nesting of interfaces.
Interfaces that do not contain other interfaces are referred to as simple interfaces.
Use
A compound interface is a specialization of its component interfaces. Component interfaces, as well as having their individual uses, can be combined to specify a new interface.
Prerequisites
All of the component interfaces must already exist in the class library.
Procedure
Result
All of the component interfaces that you entered belong to the same nesting level. When a class uses a compound interface, it must implement all methods of all component interfaces.
The component interfaces are implemented equally, regardless of their nesting level ("flat hierarchy"). You access their components using their original names, that is, the form:
<Interface name>~<component>