title: Parsing an XML structure to perform specific operations
body: <p>I have to parse a xml structure recursively and perfrom few operations as and when i encounter a particular node.
  Which would be a good design pattern or approach for this scenario.</p>
  
  <p>ex: </p>
  
  <pre><code>&lt;Start&gt;
  
  &lt;step1&gt;
   // some data
  &lt;/step1&gt;
  
  &lt;step2&gt;
  // some data
  &lt;/step2&gt;
  &lt;step3/&gt;
  &lt;step4/&gt;
  ...
  
  &lt;/Start&gt;
  </code></pre>
  
  <p>i want to parse this whole xml and perfrom specific operations for specific steps
  For instance step-1 perform addition , for step-2 perform subs and so on</p>