Layering

... With an exception:

    <foo
      xmlns:a="http://example.com/~joe"
      xmlns:b="http://example.com/%7Ejoe"
      xmlns:c="http://example.com/&#x7e;joe"
      xmlns:d="http://example.com/&#x7E;joe"
      xmlns:e="http://example.com/&#126;joe">

Which namespace is not like the others?