Populating Tree with External XML File

Question

I want to use external files for populating Flex 3
components. I have been successful using code very similar to that
below for a data grid & for a combo box, but it won't work for
a tree. Can you determine wh?
<?xml version="1.0" encoding="utf-8"?>
<mx:WindowedApplication xmlns:mx="
http://www.adobe.com/2006/mxml"
layout="absolute">
<mx:HTTPService id="dp_Tree1" url="Tree1.xml" />
<mx:Tree dataProvider="{dp_Tree1.lastResult.root.node}"
creationComplete="dp_Tree1.send()" width="333"/>
</mx:WindowedApplication>
It's not working & I can't determine why. Attached is my
xml file that I tested it with.

Answer 1

Thanks a bunch folks, but my intent is to have as little code
as possible. I want to help people who are not coders create
designs using external xml files to populate controls. I was able
to create very simple code with just two lines to populate a
DataGrid from an external xml file:
<mx:HTTPService id="dp_DataGrid1" url="DataGrid1.xml"
/>
<mx:DataGrid
dataProvider="{dp_DataGrid1.lastResult.component.rows}"
creationComplete="dp_DataGrid1.send()" />
And just two lines for a ComboBox:
<mx:HTTPService id="dp_ComboBox1" url="ComboBox1.xml"
/>
<mx:ComboBox
dataProvider="{dp_ComboBox1.lastResult.component.rows}"
creationComplete="dp_ComboBox1.send()" />
Isn't it possible to populate a tree with two lines like as
it is with a DataGrid & ComboBox?