XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (396 page)

A
NameTest
of the form
*:code
matches any node whose local-name is
code
, regardless of its namespace (it will match names in any namespace, as well as names that are in no namespace).

The
NameTest
xyz:code
matches any name whose namespace is the one currently bound to the namespace prefix
xyz
and whose local part is
code
. Again, the name being tested doesn't need to use the same prefix, provided it refers to the same namespace URI.

The interpretation of a
NameTest
such as
code
(with no namespace prefix) depends on the context:

• If it is used with any axis other than the attribute or namespace axes, then it selects elements whose name is in the namespace identified in the XPath context (see Chapter 7) as the default namespace for element and type names. In XSLT, this is established using the
  [xsl:]xpath-default-namespace
  attribute, typically on the
  
  element. It is not affected by a default namespace declaration of the form
  xmlns=“some.uri”
  .
  
• If it is used with the attribute or namespace axis, then it selects nodes whose namespace URI is null.