OSGi Concepts Modules
Modules layer defines the class loading policies.
The OSGi Framework is a powerful and rigidly specified class-loading model. It is based on top of Java but adds modularization. In Java, there is normally a single classpath that contains all the classes and resources. The OSGi Modules layer adds private classes for a module as well as controlled linking between modules. The module layer is fully integrated with the security architecture, enabling the option to deploy closed systems, walled gardens, or completely user managed systems at the discretion of the manufacturer.