A direct connection to an OPC UA server is definitely the preferred scenario as this allows us to make the most of the features and capabilities of OPC UA. It can be deployed in two different ways. In the first setup, the edge is directly connected to the OPC UA server by means of its OPC UA client interface:

The data source can be one of the ones analyzed previously: a PLC, a DCS, a SCADA system, or a Historian. OPC abstracts the data source, which is why, in the preceding diagram, the OPC UA server shows a dotted link for each of these potential data sources. Obviously, in this scenario, like in the previous one, the OPC server must be specific for that data source, but from the client's perspective and from the point of view of the edge, this does not matter.