Is <part> all-or-nothing? (XInclude problem?)

[Larry Garfield <larry@garfieldtech.com>]

Here's a weird one. :-)

I have a book I'm putting together where each chapter/article is a separate 
file referenced via XIncludes.  No sweat, right?  The following for the 
book.xml file works just fine:

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

However, if I try to add <part> elements then it fails:

<book id="charters">
 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"; href="preface.xml" />
 <part>
  <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"; href="gmd.xml" />
 </part>
</book>

(It fails regardless of whether or not I specify a title element for the 
part.)

However, if I put BOTH XIncludes inside part elements (the same or different), 
then it works fine again:

<book id="charters">
 <part>
  <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"; href="preface.xml" />
 </part>
 <part>
  <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"; href="gmd.xml" />
 </part>
</book>

The error I'm getting is the most confusing part:

Error reported by XML parser: Elements from namespace 
'http://www.w3.org/2001/XInclude', other than 'fallback', are not allowed to 
be children of 'include' elements.  However, 'include' was found.

What does the number of part elements have to do with XInclude, and why is it 
claiming I have an include element inside an include element when I clearly 
don't?  Neither of the included files have any XIncludes of their own, so 
that's not the problem.

Can you not have chapters or articles that are not part of a <part> if you use 
<part> at all?  That seems to be what is happening, but it doesn't look like 
that's the case according to the spec.  It also wouldn't make sense, as a 
preface (I am using a <preface> element in preface.xml) isn't really a part 
of a <part>.  It's a preface.  

Can anyone shed some light on what's happening here?

-- 
Larry Garfield			AIM: LOLG42
larry@garfieldtech.com	ICQ: 6817012

"If nature has made any one thing less susceptible than all others of 
exclusive property, it is the action of the thinking power called an idea, 
which an individual may exclusively possess as long as he keeps it to 
himself; but the moment it is divulged, it forces itself into the possession 
of every one, and the receiver cannot dispossess himself of it."  -- Thomas 
Jefferson