Is it Impossible to Keep up to Date?

Two different types of updates of information states are distinguished corresponding to two different kinds of incoming information: information about the actual state of domain; and information about changes made to the state of that domain. Gardenfors [1986] proves a theorem showing that the first kind of update function can have certain intuitively appealing properties only on pain of triviality. Here a similar trivialisation result is proved for the second kind of update function.