ModuleControl is optionally implemented by a module's factory class.
The monitor provides a central registry for all modules in the system, and manages loading, starting, and finding them.
Allows a module to check its environment before it is selected as an implementation.
A PersistentService modularises the access to persistent services, abstracting out details such as finding the list of services to be started at boot time, finding the service.properties file and creating and deleting the persistent storage for a service.
A service is a collection of modules that combine to provide the full functionality defined by the service.