UML14 — Generalized change events

Summary: The expressive power of change-events is limited. We are writing a
specification that is much simpler if we can trigger transitions under a
circumstance like the following:

"P has just become true and it is not the case that Q has just
become true"

There"s no way to say that with a change-event. Instead we have to write a
somewhat obscure sequence of transitions that defines a program to calculate
this.

Considered and declined.