How do I use the default XML namespace to refer to attribute names in an XML namespace?
You can’t. The default XML namespace only applies to element type names, so you can refer to attribute names that are in an XML namespace only with a prefix. For example, suppose that you declared the http://www.tu-darmstadt.de/ito/addresses namespace as the default XML namespace. In the following, the type attribute name does not refer to that namespace, although the Address element type name does. That is, the Address element type name is in the http://www.tu-darmstadt.de/ito/addresses namespace, but the type attribute name is not in any XML namespace.