title: What does different namespaces mean in Flex?
body: <p>I worked on a flex application 6-7 months back. We used flex 3.5 sdk. Now we are upgrading our flex app with flex sdk 4/4.1 </p>
  
  <p>I am still new to flex development and I have a very basic question related to namespace. </p>
  
  <p>I have seen three different namespaces in flex sample applications. What is the purpose of having three diff namespaces? When do I use each of them ?</p>
  
  <pre><code>xmlns:fx="http://ns.adobe.com/mxml/2009" 
  xmlns:s="library://ns.adobe.com/flex/spark" 
  xmlns:mx="library://ns.adobe.com/flex/mx"
  </code></pre>
  
  <p>Thanks</p>