From the definition it is clear that SubDevice is a virtual view of the workspace of a physical device. Many devices supports several work groups with the same functions. Each work group can be located in a separate zone. For full control over the zone SubDevice is created for each work group of the device. For example, 6-channels HDL dimmer contains 6 dimmable channels that can control 6 work groups. That's why, it is reasonable to create 6 SubDevices in the module to be able to create actions, events and conditions for each work group separatelly. SubDevices in i3 lite modules are compulsory, their number can vary from 1 to many. Usually the number of SubDevices is equal to the number fo controller channels.