me : true, updateGroup: false, remove: false}</code>.
  </p>

  <p>
    One can specify callback functions to validate changes made by the user. There are a number of callback functions for this purpose:
  </p>

  <ul>
    <li><code>onAdd(item, callback)</code> Fired when a new item is about to be added. If not implemented, the item will be added with default text contents.</li>
    <li><code>onUpdate(item, callback)</code> Fired when an item is about to be updated. This function typically has to show a dia