The HMI client is a standard Web browser (currently only Internet Explorer is available for this use) that receives and displays data from HMI Server, which is the HMI client’s interface with Data Server. A special feature of the HMI client is that it is a thin client , meaning that no additional software is required for it to carry out the above function, significantly reducing the total cost of ownership. As a basic security feature, data access is limited depending on user privilege, and an optional operation shield package is available that restricts access via keyboard commands to critical system operations such as system shutdown. An additional feature of this package is the always-on foreground display of specified windows, turning the PC running this software into a dedicated HMI client PC.