what is usecase bubbling
LOL, I guess your guess is as good as mine. I am not aware of a official term or what it is in the UML context.
I believe the term bubbling is blown over from Java coding. I am not a java coder but it has something to do with catching exceptions, if you do not include a try/catch statement, the exception will bubble to the top of the method in witch appeard and is tossed to the method caller. The reason is that the exception continues to propagate the call stack.
Doing so the exception bubbles up until it’s caught, or until it pops out of the application and terminating with the good old error message.
That is the only bubbling I am aware of that might relate to this, like I said I do not believe it is an “official” UML Term.
Hope this helps,