Question

I need to extract (XSLT, xpath, xquery… Preferably xpath) the most deeply nested element nodes with method (DEST id=”RUSSIA” method=”delete”/>) and his direct ancestor (SOURCE id=”AFRICA” method=”modify”>).

I don’t want to get the top nodes with methods ( main method=”modify”> or main method=”modify”> ).

The deepest nested elements with method correspond to real actions.
The top elements with method actually are dummy actions that must not be taken into account.

Here is my XML sample file:

<?xml version="1.0" encoding="UTF-8"?>
<main method="modify">
<MACHINE method="modify">  
  <SOURCE id="AFRICA" method="modify">
    <DEST id="RUSSIA" method="delete"/>
    <DEST id="USA" method="modify"/>
  </SOURCE>

  <SOURCE id="USA" method="modify">
    <DEST id="AUSTRALIA" method="modify"/>
    <DEST id="CANADA" method="create"/>
  </SOURCE>
</MACHINE>
</main>

This is Xpath output I expect:

<SOURCE id="AFRICA" method="modify"><DEST id="RUSSIA" method="delete"/>

<SOURCE id="AFRICA" method="modify"><DEST id="USA" method="modify"/>

<SOURCE id="USA" method="modify"><DEST id="AUSTRALIA" method="modify"/>

<SOURCE id="USA" method="modify"><DEST id="CANADA" method="create"/>

My current xpath command does not provide the adequate result.

Command xpath(“//[@method]/ancestor::*”) which is returning:

<main><MACHINE method="modify">                                        # NOT WANTED

<MACHINE method="modify"><SOURCE id="AFRICA" method="modify">          # NOT WANTED

<MACHINE method="modify"><SOURCE id="USA" method="modify">             # NOT WANTED

<SOURCE id="AFRICA" method="modify"><DEST id="RUSSIA" method="delete"/>

<SOURCE id="AFRICA" method="modify"><DEST id="USA" method="modify"/>

<SOURCE id="USA" method="modify"><DEST id="AUSTRALIA" method="modify"/>

<SOURCE id="USA" method="modify"><DEST id="CANADA" method="create"/>

My xmltwig code for additional information (context):

#!/usr/bin/perl -w
use warnings;
use XML::Twig;
use XML::XPath;

@my $t= XML::Twig->new;
my $v= XML::Twig::Elt->new;
$t-> parsefile ('input.xml');

@abc=$t->get_xpath("\/\/[\@method]\/ancestor\:\:\*") ;
 foreach $v (@abc)   # outer 1
 {
    foreach $v ($v ->children)  # internal 1
    {
      $w=$v->parent;
      print $w->start_tag;
      print $v->start_tag;
    }
  }

Answer 1

The nodes with maximum depth can be found with

//*[count(ancestor::*) = max(//*/count(ancestor::*))]

but it might perform horribly, depending how smart your optimizer is.

Having found those nodes, it is of course trivial to find their ancestors. But you are looking for output with more structure than XPath alone can provide.