industrial//industrial data layer//OPC

One of the historic problems of automation was that every vendor exposed its data differently, so a SCADA would have needed to implement every industrial protocol. **OPC** appeared as a standard interface to industrial data: the vendor or integrator implements an OPC server for the PLC, and the SCADA, MES or historian talk OPC to that server instead of the proprietary protocol.

One of the historic problems of automation was that every vendor exposed its data differently, so a SCADA would have needed to implement every industrial protocol. OPC appeared as a standard interface to industrial data: the vendor or integrator implements an OPC server for the PLC, and the SCADA, MES or historian talk OPC to that server instead of the proprietary protocol.

The original OPC, now called OPC Classic, and its data-access profile OPC DA were tied to Microsoft COM and DCOM. It worked on Windows and suffered exactly the problems of that dependency: Windows only, painful DCOM configuration, weak security, firewalls and interoperability. "Windows old" is a fair summary.

Its successor, OPC UA, dropped COM/DCOM and added an information model. The idea of a server in front of the controller survived both generations, and it is now also a role of the edge gateway.