There is often an ambiguity between things that should occur in response to change of state of a boolean versus things that may occur while a boolean is in a certain state. I call this ambiguity WhenAndWhile.

One useful way to resolve the ambiguity is to rigorously use "When" to refer to the transition, and specifically to the instant when the transition begins, and to use "While" to refer to a duration, and therefore to the period that a boolean stays in a state.

Thus, "
''when''
the activityCompleted event is asserted" means the instant when the event is notified, and "
''while''
the activityCompleted event is asserted" means the duration during which the event is being handled.

This is especially helpful in working through notification chains, where the distinction between an instant and a duration is often important.

--TomStambaugh