x:include and namespace

Hello, I am sure I am doing something wrong here or I don't understand 
the xml namespace.
I have a main document that consist of chapter included using Xinclude 
and each chapter uses Xinclude to get codes and examples.
Now, it the root of the main document I declared the xinclude namespace, 
and I did the same for the root of each chapter, but it's failing to 
generate fo successfully because x:include  has no template match !
This is the output



Buildfile: build.xml

fo:
     [java] file:///opt/docbook/fo/docbook.xsl; Line #316; Column #16; 
Making portrait pages on USletter paper (8.5inx11in)
     [java] file:///opt/docbook/fo/docbook.xsl; Line #97; Column #16; 
xi:include encountered in book, but no template matches.
     [java] file:///opt/docbook/fo/docbook.xsl; Line #97; Column #16; 
xi:include encountered in book, but no template matches.
     [java] file:///opt/docbook/fo/docbook.xsl; Line #97; Column #16; 
xi:include encountered in book, but no template matches.

BUILD SUCCESSFUL
Total time: 39 seconds

If i include the namespace address with every xinclude tag, then it 
works. In other words, if I do this
=============================================================
<chapter id="ch1" xmlns:xi="http://www.w3.org/2003/XInclude" 
xmlns:mml="http://www.w3.org/1998/Math/MathML" >

.......

<programlisting>
                <xi:include href="code/c1.txt" parse="text"  />
            </programlisting>
=================================================
Then, it will fail but if I add 
xmlns:xi="http://www.w3.org/2003/XInclude" to x:include tag then it will 
be generate fine.  I thought using the prefix to indicate a namespace is 
sufficient.