Validated Xinclude'd file

Hello, 

If you have an included file, e.g. Docbook5 chapter included in Docbook5 book, which has no DTD, and not a valid root element on its own, is there a way to have it validated?

In other words, is there a way to get nXML mode to validate a standalone chapter document? 

book.xml (nXML valid - using docbookxi.rnc):
<?xml version="1.0" encoding="utf-8"?>
<book xmlns="http://docbook.org/ns/docbook"
      xmlns:xi="http://www.w3.org/2001/XInclude">
<title>My First Book</title>
<xi:include href="chap1.xml"/>
</book>

chap1.xml (nXML Invalid - using docbookxi.rnc):

<?xml version="1.0" encoding="utf-8"?>

<chapter id="ch1"><title>My First Chapter</title>
<para>My first paragraph.</para>




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