xinclude conditionally

[Georges Schmitz <georges.schmitz@arcor.de>]

what is the best way to conditionally include xml documents by using 
Xinclude. We have in DocBook a standard attribute called "condition" and 
I would like to use it directly in <xi:include> (see below). Or have I 
to set the attribute necessarily in the root element of the included 
document?


My wish:

  <xi:include
    xmlns:xi="http://www.w3.org/2003/XInclude";
    href="art-tutorial.xml"
    parse="xml"
    condition="tutorial"               
    >
    <xi:fallback>
      <para>
        <emphasis role="bold">FIXME: missing xinclude content 
(metadata)</emphasis>
      </para>
    </xi:fallback>
  </xi:include>