title: diff two XML files
body: <p>I have xml document like this:</p>
  
  <pre><code>&lt;datatypes xmi:id="ID_01"&lt;/datatypes&gt;
  &lt;datatypes xmi:id="ID_02"&gt;
    &lt;fields xmi:id="ID_03"&gt;
      &lt;datatype xmi:idref="ID_01"&gt;&lt;/datatype&gt;
    &lt;/fields&gt;
  &lt;/datatypes&gt;
  </code></pre>
  
  <p>I also have spesil tool that change xml files. It allows you to add new nodes atributes and change old one, but after use it all IDs change.</p>
  
  <p>Afte use tool:</p>
  
  <pre><code>&lt;datatypes xmi:id="ID_11"&lt;/datatypes&gt;
  &lt;datatypes xmi:id="ID_12"&gt;
    &lt;fields xmi:id="ID_13"&gt;
      &lt;datatype xmi:idref="ID_11"&gt;&lt;/datatype&gt;
    &lt;/fields&gt;
    &lt;something_new/&gt;
  
  &lt;/datatypes&gt;
  </code></pre>
  
  <p>I want compare two xml files and find only <strong>&lt; something_new/></strong>. When i use standart diff i see all changes (id too)</p>
  
  <p>Are there easy way to solve this problem?
  if not, what langudge(IDE) I should use for write such a comparison fastert.</p>