Subscribe operations can only be executed as calls from an asynchronous connector, as these use a websocket connection in the background to push changes from the Simplifier Server to the Business Application.

operationType: Defines which operation you want to execute, in this case, “SUBSCRIBE”.
Parameter Name: operationType
Constant Value: SUBSCRIBE
Data Type: String

subscriptionType: Specifies the OPC UA Node type, that the subscription monitors
Parameter Name: subscriptionType
Constant Value: VARIABLE, EVENT
Data Type: String

nodeId: Defines the identification of the OPC UA node. It is split in 3 parameters (two mandatory and one optional):

• identifier:
  Parameter Name: nodeId/identifier
  Data Type: String
• namespaceIndex:
  Parameter Name: nodeId/namespaceIndex
  Data Type: Integer
• identifierType (optional): Searches for the Identifier with a fixed Data Type.
  Parameter Name: nodeId/identifierType
  Data Type: String
  Constant Value: Numeric, UUID, String, Byte String

Note: In every namespace, each ID must be unique for its own identifierType (it is possible to use the String “7617” and the Numeric 7167 together in one namespace)

monitoredItems: Specifies a list of NodeIDs to be monitored
Parameter Name: monitoredItems[ ]
Data Type: Any (depends on the concrete child element within the parameter path)

Example of a monitored item for subscriptionType Variable:

monitoredItems[0]/identifier
monitoredItems[0]/namespaceIndex

Example of a monitored item for subscriptionType Event:

monitoredItems[0]/eventType/identifier
monitoredItems[0]/eventType/namespaceIndex
monitoredItems[0]/nodeId/identifier
monitoredItems[0]/nodeId/namespaceIndex

Output parameters

You can return all output parameters like this:

Parameter Name: /
Alias: result
Data Type: Any

If you want to get only selected output values, use the following syntax:

Parameter Name: value (for type variable) or data (for type event)
Data Type: float (depends on the values you want to be returned)