[RFC] Include xhtml like xinclude in docbookxi.rng?

[RFC] Include xhtml like xinclude in docbookxi.rng?

When I validate defguide5-en.xml, the following errors occurred:

C:\wc\svn\docbook\defguide5\en\build>java -jar jing.jar docbook.rng
defguide5-en.xml

C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:22269: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:22391: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:22636: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:22758: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:44278: error:
unknown element "form" from namespace "http://www.w3.org/1999/xhtml"
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:44280: error:
unknown element "input" from namespace "http://www.w3.org/1999/xhtml"
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:44281: error:
unknown element "input" from namespace "http://www.w3.org/1999/xhtml"
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:44282: error:
unknown element "input" from namespace "http://www.w3.org/1999/xhtml"
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:44283: error:
unknown element "input" from namespace "http://www.w3.org/1999/xhtml"
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:44284: error:
unknown element "input" from namespace "http://www.w3.org/1999/xhtml"
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:53921: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:53980: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:53984: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:54048: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:54068: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:54332: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:103459: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:103518: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:103522: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:103622: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:103642: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:103998: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:105954: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:106080: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:107201: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:107334: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:110942: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:111077: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:112566: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:112699: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:113400: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:113531: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:116500: error:
unfinished element
C:\wc\svn\docbook\defguide5\en\build\defguide5-en.xml:116621: error:
unfinished element

Any suggestion?

Dongsheng