XML Namespaces and Unprefixed Attributes

Solution 1:

The normal interpretation used by XPath and other specs is that an unprefixed attribute is in no namespace.

There are language lawyers who will insist that the namespaces spec doesn't say that. It says that an unprefixed attribute is in whatever namespace the designer of the vocabulary says it is in. But this interpretation isn't very useful in practice; it's what the tools do that matters.

Solution 2:

An attribute without prefix is always in the empty name space, i.e. it has no name space. It is doesn't matter whether the enclosing element has a name space or not. That's my reading of the second statement you refer to, and that is the interpretation of all the XML tools I've used.