   // default callback action for measurement messages not registered above
   fileprivate var defaultMeasurementCallback : TargetAction?
   // dictionary holding last received measurement message for each measurement type
-  fileprivate var latestVehicleMeasurements: NSMutableDictionary! = NSMutableDictionary()
+  fileprivate var latestVehicleMeasurements = [NSString:VehicleMeasurementResponse]()
   
   // dictionary for holding registered diagnostic message callbacks
   // pairing bus-id-mode(-pid) String with callback action

          rsp.event = event
          
          // capture this message into the dictionary of latest messages
          latestVehicleMeasurements.setValue(rsp, forKey:name as String)
          
          // look for a specific callback for this measurement name
          var found=false

      }

      // clear any saved context
      latestVehicleMeasurements.removeAll()
      
      // update the connection state
      connectionState = .connectionInProgress
