xf Namespace

XQuery/XPath issue 228 & XSLT issue 155 state that built-in functions 
are in the F&O namespace with no controls on changing that namespace.  
In the 11/15/02 draft, I assumed that "xf" was used to refer to this 
namespace (though, it was not listed among the predefined namespaces in 
Namespace Declarations 
<http://www.w3.org/TR/2002/WD-xquery-20021115/#id-namespace-decls>).

While I was looking at the 5/2/3 XQuery Use Cases 1.9.4.3 Q3 
<http://www.w3.org/TR/2003/WD-xquery-use-cases-20030502/#d0e2160>, I 
noticed that built-in string manipulation function "starts-with" was 
qualified with the "xf" namespace.  Is this a typo or is this still 
necessary?  Did one of the imports change the default namespace for 
built-in functions?  If "xf" is still a valid namespace, then shouldn't 
it be added to the list of predefined namespace in the 5/2/3 Namespace 
Declarations <http://www.w3.org/TR/xquery/#id-namespace-decls>?