What is deregistration, and why is it needed?
Deregistration removes a particular device from a domain (group of devices) with which it was grouped when it was registered. The purpose of deregistration is to support models where the number of registered devices or applications is limited. When the maximum number is reached, a user can deregister some devices (for example devices that are lost, no longer in use, etc.) in order to be able to register new ones. When a device is deregistered, the Link established during registration (e.g., a Link from a Personality Node to a User Node) is invalidated. This prevents the device from using that Link to access content whose License specifies that that particular User Node must be reachable from the device.
