Past experience with OPC(going back 20 years)is that the OPC client needs to connect to a OPC server that is then connected to the field devices to get tag data. In other word, for a PLC, it would have to be programmed, compiled, and running to get tag data to OPC. For modern systems, OPC UA is the choice, but it looks like the same limitations apply. There is a standard for importing and exporting tags via an XML NodeList. Does anyone know of any PLC's or HMI's that utilize offline OPC UA tag import and export? For HMI's, I am primarily interested in traditional machine mounted touchscreens, not PC-based SCADA systems.