A Topic is a string associated with a NetworkMessage that can be used to logically organize NetworkMessages published to a Message Oriented Middleware. Topics are most commonly used with Broker-based middleware where the filtering is done by the Broker. However, Topics can be used with Broker-less middleware where the filtering is done by the Subscriber.

Topics have a hierarchical structure with different Topic levels separated by a delimiter like ‘/’. For example:

opcua/json/status/FlowController1

Mappings to different implementation technologies may add additional constraints.

A Topic for NetworkMessages containing DataSetMessages is typically used as QueueName for the broker-based communication configuration.