cannot get XInclude to work

[Sam Steingold <sds@gnu.org>]

Hi,
I am forced to use xinclude because a file I used to include using a
system entity now contains <!DOCTYPE> and thus can only be included
using xinclude.
my toolchain is xmllint+xsltproc.
I use docbook 4.5.

so, my main file now says:
===================================
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"  "..." [
...
]>

<book id="impnotes-top"
      xmlns="http://docbook.org/ns/docbook";
      xmlns:xi="http://www.w3.org/2001/XInclude";>
 <title>Implementation Notes for &gnu; &clisp;</title>

.....

<xi:include href="http://www.gnu.org/licenses/fdl.xml";>
 <xi:fallback><appendix id="gfdl"><title>GNU Free Documentation License</title>
   <para>internet connection to the &fsf; is broken</para></appendix>
</xi:fallback></xi:include>
<xi:include href="http://www.gnu.org/licenses/gpl2.xml";>
 <xi:fallback><appendix id="gpl"><title>GNU General Public License</title>
   <para>internet connection to the &fsf; is broken</para></appendix>
</xi:fallback></xi:include>

....
===================================

alas, I cannot validate:

$ xmllint --xinclude --noout --valid --postvalid --timing --noent impnotes.xml
impnotes.xml:49: element book: validity error : No declaration for
attribute xmlns of element book
      xmlns:xi="http://www.w3.org/2001/XInclude";>
                                                ^
impnotes.xml:49: element book: validity error : No declaration for
attribute xmlns:xi of element book
      xmlns:xi="http://www.w3.org/2001/XInclude";>
                                                ^
impnotes.xml:219: element include: validity error : No declaration for
attribute href of element include
<xi:include href="http://www.gnu.org/licenses/fdl.xml";>
                                                      ^
impnotes.xml:222: element fallback: validity error : No declaration
for element fallback
</xi:fallback></xi:include>
              ^
impnotes.xml:222: element include: validity error : No declaration for
element include
</xi:fallback></xi:include>
                           ^
impnotes.xml:223: element include: validity error : No declaration for
attribute href of element include
<xi:include href="http://www.gnu.org/licenses/gpl2.xml";>
                                                       ^
impnotes.xml:226: element fallback: validity error : No declaration
for element fallback
</xi:fallback></xi:include>
              ^
impnotes.xml:226: element include: validity error : No declaration for
element include
</xi:fallback></xi:include>
                           ^
impnotes.xml:228: element part: validity error : Element part content
does not follow the DTD, expecting (beginpage? , partinfo? , (title ,
subtitle? , titleabbrev?) , partintro? , (appendix | chapter | toc |
lot | index | glossary | bibliography | article | preface | refentry |
reference)+), got (title appendix xi:include xi:include )
</part>
       ^
Parsing took 527 ms
http://www.gnu.org/licenses/gpl2.xml:1: validity error : Validation
failed: no DTD found !
<appendix id="gpl">
                  ^
Xinclude processing took 207 ms
impnotes.xml:49: element book: validity error : No declaration for
attribute xmlns of element book
impnotes.xml:49: element book: validity error : No declaration for
attribute xmlns:xi of element book
impnotes.xml:216: element part: validity error : Element part content
does not follow the DTD, expecting (beginpage? , partinfo? , (title ,
subtitle? , titleabbrev?) , partintro? , (appendix | chapter | toc |
lot | index | glossary | bibliography | article | preface | refentry |
reference)+), got (title appendix section appendix )
impnotes.xml:73: element xref: validity error : IDREF attribute
linkend references an unknown ID "gfdl"
Document impnotes.xml does not validate
Validating took 120 ms
Freeing took 81 ms
make: *** [check] Error 3

-- 
Sam Steingold <sds@gnu.org>