Abstract: A method of performing a control operation on a target apparatus in a network including a step of creating a function information file describing control functions of the target apparatus, a step of forming a control window by gathering control functions stored in the function information file, a step of storing the control window in a performance information file, and a step of performing control operations by retrieving the control window from the performance information file. The method prepares beforehand the function information file that stores information of various functions of the target apparatuses and their platforms. The window for controlling the target apparatuses can be created by cutting and pasting necessary control functions from the function information file to the control window. The control functions created in the window are stored in the performance information file. A function performance unit retrieves a control function to perform the control operation accordingly.