[Name] target [Required] false [Type] Value expression [Default Value] the current session [Valid Values] A valid target URL [Description] 
A value expression returning a unique identifier of the message target that the platform should send the event to. See 8.3 Legal Data Values and Value Expressions for details. If the special value '_internal' is specified, the event is added to the internal event queue of the current session. If no value is specified, the event is added to the external event queue of the current session.