A plurality of controller devices connected to a network constructed by a serial bus interface, for controlling at least one controlled device to be controlled which is also connected to the network, wherein
- each controller device comprises memory means for possessing controller software for controlling the controlled device, and
- each controller device answers a capacity of the memory means to a manager device in response to an inquiry from the manager device which manages device operation on the network, and stores control software assigned by the manager device into the memory means;
- wherein if it is impossible to assign the control software, the controller device deletes unnecessary control software stored in the memory means, based on an instruction from the manager device, and stores the control software into the memory means;
- further comprising possession determination means for determining whether or not the unnecessary control software is stored in the memory means, based on an instruction from the manager device, if the control software is of a controlled device of a desired function.