The StreamInsight Extensions for OPC Data Client provide OPC event sources in form of OPC observables, i.e. .NET reactive object with  IObservable interface. In order to simplify creation of these OPC event sources, static classes with various overloads of Create method are provided:

• In order to create OPC Data Access event source, call one of the DAItemChangedObservable.Create<TValue> method overloads, passing it arguments such as the OPC server ProgID, OPC item ID, and requested update rate.
• In order to create OPC Alarms and Events event source, call one of the AENotificationObservable.Create method overloads, passing it arguments such as the OPC server ProgID, notification rate, and subscription filter.
• In order to create OPC Unified Architecture (data) event source, call one of the UADataChangeNotificationObservable.Create<TValue> method overloads, passing it arguments such as the OPC server endpoint, OPC node ID, and sampling interval.

For more information and details on the OPC Observables, see the appropriate chapters (separately for OPC-DA, OPC-A&E, and OPC-UA) in the Reactive Programming Model section of this document.