In PubSub the participating OPC UA Applications with their roles as Publishers and Subscribers are decoupled. The number of Subscribers receiving data from a Publisher does not influence the Publisher. This makes PubSub suitable for applications where location independence and/or scalability are required.
The following are some example uses for PubSub:
- Configurable peer-to-peer communication between controllers and between controllers and HMIs. The peers are not directly connected and do not even need to know about the existence of each other. The data exchange often requires a fixed time-window; it may be point-to-point connection or data distribution to many receivers.
- Asynchronous workflows. For example, an order processing application can place an order on a message queue or an enterprise service bus. From there it can be processed by one or more workers.
- Logging to multiple systems. For example, sensors or actuators can write logs to a monitoring system, an HMI, an archive application for later querying, and so on.
- OPC UA Servers representing services or devices can stream data to applications hosted in the cloud. For example, backend servers, big data analytics for system optimization and predictive maintenance.