XMLType and Namespace problem

I've run into some strange problem with XMLType and XML namespaces. I'll try to make a showcase. Lets define variable and simple XML content

SQL> var x varchar2(200);
SQL> exec :x := '<feed
xmlns="http://www.w3.org/2005/Atom"><id>test_id</id></feed>'
PL/SQL procedure successfully completed.

Try to find out what tag is on root:

SQL> select XMLType(:x).getRootElement() from dual;
XMLTYPE(:X).GETROOTELEMENT()
--------------------------------------------------------------------------------
feed

Lets find out the namespace:

SQL> select XMLType(:x).getNamespace() from dual;
XMLTYPE(:X).GETNAMESPACE()
--------------------------------------------------------------------------------

Seems to be no namespace. But there was namespace in XML definition. Lets try extract data:

SQL> select XMLType(:x).extract('/feed').getStringVal() from dual;
XMLTYPE(:X).EXTRACT('/FEED').GETSTRINGVAL()
--------------------------------------------------------------------------------

So nothing was extracted. It's not what I was expecting. Ok, lets try to force namespace:

SQL> select XMLType(:x).extract('/feed',
'xmlns="http://www.w3.org/2005/Atom"').getStringVal() from dual;
XMLTYPE(:X).EXTRACT('/FEED','XMLNS="HTTP://WWW.W3.ORG/2005/ATOM"').GETSTRINGVAL(
--------------------------------------------------------------------------------
<feed
xmlns="http://www.w3.org/2005/Atom"> <id>test_id</id>
</feed> 

Now works fine.
For me it is little confusing: there is no namespace, but you must provide namespace if you want to extract data.
Paweł