I would like to process several input sources as one xml tree. Like this:

<?xml version="1.0" encoding="UTF-8"?>
<takenotes>
<include buffer="notes-example"/>
<include file="notes-example.xml"/>
</takenotes>

with the sources having the structure
<notes>
<note>...</note>
...
</notes>

and the code for <takenotes> containing:
read from all sources given on <include>-notes
afterwards process all content at once

Thus the content of the various source should be read into one tree to be processed, but I cannot get this done.
How to amalgam this separate sources into one?

Hans van der Meer