Ah good. I don't use XML::Twig, so I don't have a deep knowledge of it.

If it consistently ignored namespaces when map_xmlns isn't used, it would be a great shortcut despite being non-standard since there is rarely need to deal with namespace conflicts. (The module never claimed them to be a real XPaths.) Unfortunately, it doesn't consistently ignore namespaces.

On the plus side, it works according to standard when map_xmlns is used. (Well, I'm not sure how namespaces interact with attributes, so I'm simply commenting on elements.)

use strict;
use warnings;

use XML::Twig qw( );

my $xml = <<'__EOI__';
<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<root xmlns:foo="uri:foo">
  <ele id="a" />
  <ele id="b" xmlns="uri:foo"/>
  <foo:ele id="c" />
</root>
__EOI__


{
   my $seen = '';

   my $t = XML::Twig->new(
      twig_handlers => {
         'ele' => sub { $seen .= $_->att('id') },
      },
   );
   $t->parsestring($xml);

   print("$seen\n");
   print($seen eq 'a'                   ? "Standard\n"   : "Not standa
+rd\n");
   print($seen eq 'a' || $seen eq 'abc' ? "Consistent\n" : "Not consis
+tent\n");
}

print("\n");

{
   my $seen_null = '';
   my $seen_foo  = '';

   my $t = XML::Twig->new(
      map_xmlns => {
         'uri:foo' => 'f',
      },
      twig_handlers => {
         'ele'     => sub { $seen_null .= $_->att('id') || $_->att('f:
+id') },
         'f:ele'   => sub { $seen_foo  .= $_->att('id') || $_->att('f:
+id') },
      },
   );
   $t->parsestring($xml);

   print("$seen_null:$seen_foo\n");
   print($seen_null eq 'a'                        ? "Standard\n"   : "
+Not standard\n");
   print($seen_null eq 'a' || $seen_null eq 'abc' ? "Consistent\n" : "
+Not consistent\n");
   print($seen_foo eq 'bc'                        ? "NS working\n" : "
+NS broken\n");
}
[download]

ab
Not standard
Not consistent

a:bc
Standard
Consistent
NS working
[download]

There are actually 3 ways of dealing with namespaces, 2 of which are supported by XML::Twig:

• proper support, your second example, which is correct, but verbose as you have to associated namespace URIs to prefixes; I also suspect that it is not as robust as one would expect, I don't quite trust those URIs to not change sneakily, especially for the default namespace,
• ignore namespace declarations is XML::Twig's default mode, there foo:ele is the element by that name, and ele is just ele, whether it is assigned a default namespace or not, you think of this as inconsistent,
• drop all namespaces, which is your first example, there foo:ele is seen as ele; I had never thought of that option, I could add it, but I strongly suspect that it would be one favored only by users who care about namespaces, and already use map_xmlns (or XML::LibXML!),

For XML::Twig, consistency is not as important as convenience, and I the current behaviour seems to be convenient for most users. I'll look into adding an option to just drop namespaces, it should not be too difficult, but I am not sure how useful it would be.

There are actually 3 ways of dealing with namespace

"Drop" and "ignore" mean the same thing. At the very least, the difference is ambiguous. Let's clarify:

• Standard support (verbose)
• Ignore namespace declarations (assume everything is in the null namespace)
• Ignore namespace declarations and make prefixes significant.

The last is XML::Twig's default. It also supports the first.

For XML::Twig, consistency is not as important as convenience

That's exactly the point I was making.

Prefixes are arbitrary strings that can and do change from document to document. The employment of a default namespace also can and does change from document to document.

It would very convenient if it could ignore namespaces, but it doesn't have a way of doing that. Instead of just ignoring namespaces, the default is to make make the prefix significant. Not only is that a step in the wrong direction, it makes it unusable in theory and in practice.

Being unable to use XML::Twig under common circumstances is not convenient at all.