The Publisher is the PubSub entity that sends NetworkMessages to a Message Oriented Middleware. It represents a certain information source, for example, a control device, a manufacturing process, a weather station, or a stock exchange.
Commonly, a Publisher is also an OPC UA Server. For the abstract PubSub concepts, however, it is an arbitrary entity and should not be assumed to be an individual or even a specific network node (an IP or a MAC address) or a specific application. A Publisher may consist of one or more network nodes sending messages and management node(s) responding to discovery probe messages and providing an OPC UA Server for configuration and diagnostics.
Figure 5 illustrates a Publisher with data collection, encoding and message sending.
A single Publisher may support multiple PublishedDataSets and multiple DataSetWriters to one or more Message Oriented Middleware. A DataSetWriter is a logical component of a Publisher. See 5.4.1.2 for further information about the DataSet writing process.
If the Publisher is an OPC UA Server, it can expose the Publisher configuration in its AddressSpace. This information may be created through product-specific configuration tools or through the OPC UA defined Methods. The OPC UA Information Model for PubSub configuration is specified in Clause 9.