[Event(name="dataRequest", type=...)]
public class SomeDataViewMediator extends EventDispatcher {
   private function onDataRequestFromView(event:Event):void {
      var request:DataByModelRequest =
            new DataByModelRequest.newInstance(
                  vmRef,
                  model);
      dispatchEvent(request);
   }

   // Option 1 - use EventHandler for the response
   [EventHandler(name="dataResponse")]
   private function onDataRetrieved(response:SingleObjectDataResponse):void {
      // good to go with response.result as VmListItemData
   }

   // Option 2 - use ResponseHandler for the response
   [ResponseHandler(name="dataResponse")]
   public function onDataRetrieved(request:DataByModelRequest,
                                    result:VmListItemData,
                                    error:Error):void {
      // good to go with type-strict result
   }
}