Very important, if you are trying to parse an atom feed, say from Blogger for example. Make sure you include the following lines of code. If not, you could spend several days trying to figure out how to "trick" the system to work. I'm not saying I did this, I'm just saying it could happen...
// Define and use atom namespace
private namespace atom = "http://www.w3.org/2005/Atom";
use namespace atom;
