Get a collection of the attributes of a nodeset
===

I have a collection of nodes like this 

    <node id="1">
      <languaje>c</languaje>
      <os>linux</os> 
    </node>
    <node id="2">
      <languaje>c++</languaje>
      <os>linux</os> 
    </node>
    <node id="3">
      <languaje>c#</languaje>
      <os>window</os> 
    </node>
    <node id="4">
      <languaje>basic</languaje>
      <os>mac</os> 
    </node>

And i want to create a new collection of all the properties id's like this

    <root>
     <token>1</token>
     <token>2</token>
     <token>3</token>
     <token>4</token>
    </root>



How can do that