title: XSLT: When element exists add it and change value otherwise add element with value
body: <p>My problem is that in some xml files an element exists and in another it does not.
  When the element exists, it's value should be changed. If it does not exists, it should be added.</p>
  
  <p>Here is an example for better understanding:</p>
  
  <pre><code>&lt;root&gt;
      &lt;group&gt;
          &lt;element1&gt;SomeValue1&lt;/element1&gt;
          &lt;element2&gt;SomeValue2&lt;/element2&gt;
      &lt;/group&gt;
  &lt;/root&gt;
  </code></pre>
  
  <p>Let's say I always want element1, element2 and element3 with the values Changed1, Changed2, Changed3.</p>
  
  <p>It should end up like this:</p>
  
  <pre><code>&lt;root&gt;
      &lt;group&gt;
          &lt;element1&gt;Changed1&lt;/element1&gt;
          &lt;element2&gt;Changed2&lt;/element2&gt;
          &lt;element3&gt;Changed3&lt;/element3&gt;
      &lt;/group&gt;
  &lt;/root&gt;
  </code></pre>
  
  <p>What can I do to make it happen?<br />
  Thanking you in anticipation <br/></p>
  
  <p>Dennis</p>