With publisher/subscriber the toaster need only know to check the RequiredForBreakfast and TimeToCompletion attributes in the other app attributes files. It doesn't need to know anything at all else about the other apps and the other apps don't need to know about the toaster.

When the porridge app is added both the coffe app and the toast app can adjust their timing without any code changes because they both check for the same attributes of other apps without regard to what those apps are.