<?xml version="1.0" encoding="UTF-8" ?>
<orignal>
    <item>
        <irrelevant>junk</irrelevant>
        <relfirst>hello</relfirst>
        <relsecond>world</relsecond>
    </item>
</original>

into

<?xml version="1.0"?>
<fixed>

  <useless>0</useless>

  <fixeditem>
    <type>s</type>
    <first>hello</first>
    <second>world</second>
  </fixeditem>
</fixed>