The namespace URI (that is, the URI to which the attribute's prefix refers), or, if the name has no namespace URI, an empty string.
localname
The local (unqualified) name of the attribute.
The attribute type is one of the following strings: "CDATA," "ID," "IDREF," "IDREFS," "NMTOKEN," "NMTOKENS," "ENTITY," "ENTITIES," or "NOTATION." These are always uppercase.
Returns the Unknown value (?) if no attribute's XML qualified name matches the combination of uri and localname or if namespace processing is disabled.