Reusing <section> where a <chapter> should be - and the reverse

["Peter Desjardins" <pdesjardins@supplyscape.com>]

I often need to reuse <chapter> and <section> from one document in other
documents.  Frequently, I find that the content that I am reusing is a
<section> in one book and must be at the top level of another book.
Because <section> is not allowed at the top level of <book> and
<chapter> cannot occur anywhere except in <book>, I have trouble reusing
the content of sections and chapters in other documents.  Specifically,
I need to include the content of a <chapter> element as a child of a
<section> element.  Also I need to include the content of a <section>
element as a child of <book>.

Reading Chapter 22. Modular DocBook files in DocBook XSL led me to
believe that the following xi:include could solve the problem for me.  I
expect it to include every child element of a <section> element in the
<chapter> element.

<chapter>
    <xi:include href="docbook-file-containing-the-modular-content.xml"
                xmlns:xi="http://www.w3.org/2001/XInclude";
                xpointer="element(IdOfTheSectionElement/*)" />
</chapter>

But the xi:include fails.  I use xmllint to resolve xi:includes.  It
gives the following errors:

docbook-file-that-is-including.xml:11: element include: XInclude error :
XPointer evaluation failed: #element(IdOfTheSectionElement/*)
docbook-file-that-is-including.xml:11: element include: XInclude error :
could not load docbook-file-containing-the-modular-content.xml, and no
fallback was found

Is my xpointer syntax incorrect?  Other xi:includes from the same source
file resolved without any trouble (they include entire elements).

Is there a better way to reuse <section> and <chapter> elements in each
other's hierarchical places?

In case it matters, here's my xmllint version:

$ xmllint --version
xmllint: using libxml version 20626
   compiled with: Threads Tree Output Push Reader Patterns Writer SAXv1
FTP HTTP DTDValid HTML Legacy C14N Catalog XPath XPointer XInclude Iconv
ISO8859X Unicode Regexps Automata Expr Schemas Schematron Modules Debug


Thanks for your help!

Peter Desjardins