How to discard changes in Rules module
Create a rule for the "Content is going to be saved" event, and add a "Execute custom PHP code" action.
The code you write have access to some variables by reference: $node, $node_unchanged, $user, $author, $author_unchanged, and $user.

For example, you can use the following code to set the title as it was before the node was  edited.

$node-&gt;title = $node_unchanged-&gt;title;

return array('node' =&gt; $node);




Similar code is usable in the version for Drupal 7 of the Rules module; what changes is the variables to which the code has access.