/*

Prepare a (nested) table of contents for Book1, listing all the
sections and their titles. Preserve the original attributes of each
<section> element, if any.

*/

<toc>
   (
   LET $s := document("book.xml") 
       FILTER ( self::section OR self::title[parent::section]  OR self::text()[ parent::title/parent::section ] ) 
   RETURN $s
   )
</toc>