How to prevent a node from being saved/updated by using the Rules module? I've created a content type 'H'. The following rule (using the Rules module) has been built to prevent the node from being saved/updated if the field 'a' is larger than 5.

Event: Before saving content of type 'H'.

Condition: Data Comparison - Node field 'a' is larger than 5.

Action: Show a message on the site - Message type: Error.

Action: Go back to the front page.

It will show the error message if the condition is TRUE. However, the node is still being saved/updated.

Is it possible to control this without programming?
I'm not aware of a way to do what you're asking for by only using the Rules module ... And the (old) issue about "Prevent Node from being saved" (with confusing status "Closed (fixed)" ...) somehow seems to confirm you'd need "a bit more" ...

You can try to make it work by ALSO using the Conditional Rules module for this. Some more details about this module (from its project page):


  ... provides Rules plugins for conditionally altering execution flow directly inside a group of actions.


Here is a screenprint of a rule with an action that uses Conditional Rules (though only with an "if"-part here, no "else"):