Прошу извинить. Новичек во flex. Создаю пустой проект в flashDeveoper 4.

Код AS3:
<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx">
<fx:Declarations>
<!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>
</s:WindowedApplication>
Получаю ошибку:

Код AS3:
C:\build\book\src\Main.mxml(4): Error: Could not resolve <s:WindowedApplication> to a component implementation.
xmlns:mx="library://ns.adobe.com/flex/mx">
Build halted with errors (fcsh).
Что делаю не так?