trigger may not reference the subject relation context

  Explanation:  A BEFORE STORE or AFTER ERASE trigger or a trigger
  action  that  does  not specify FOR EACH ROW contains an illegal
  reference to the subject relation  current  or  NEW/OLD  context
  (row values or dbkey).

  User Action:  Define  the  trigger  to  use  only  the  relation
  contexts declared within the trigger actions.