OReilly and DataFormat

I have the OReilly AS 3.0 cookbook...and it has basically a code snippet similar to this one:

private function loadMenuData(){
var loader:URLLoader = new URLLoader();
loader.dataFormat = DataFormat.TEXT;
loader.addEventListener(Event.COMPLETE, loadComplete);
loader.load(new URLRequest("xml/menubar.xml"));
}

I'm getting a complier error on DataFormat: "1120: Access of undefined property DataFormat."

Any ideas why? I don't even know what package DataFormat is coming from...I guess from the net package...

Any advice would be great! Thanks in advance!