XInclude: multiple <preface>s

[Michael Wiedmann <mw@miwie.in-berlin.de>]

I try to separate a large <book> into smaller XML file using XInclude.
That works of course in general but how do I put several <prefaces>s 
into a separate XML file and XInclude it?

<book>
 <bookinfo>
 ...
 </bookinfo>

 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
   href="preface.xml" />
 
 <chapter>
 ...
 </chapter>
</book>

If 'preface.xml' contains more than one <preface> (which is IMHO valid
DocBook), then 

$ xmllint -xmllint book-master.xml > book.xml

complains like:

preface.xml:76: error: Extra content at the end of the document
<preface id="download">
^
XInclude: could not load preface.xml, and no fallback was found


Any workaround?

Michael
-- 
mw@miwie.in-berlin.de                              http://www.miwie.org
mw@miwie.org