That's okay, thanks. But it's only the beginning of my problem. How
do you describe the effect of applying a filter on top of one or more
other filters? Andrea wants to use "intersection", but I tend to
think this is too "mathematical" and too vague to explain clearly what
happens. What would be a good terminology for that?
I think there are two possibilities when adding another filter: either
broadening the already existing filtering ("union" in mathematical
terms) or narrowing the already existing filtering ("intersection" in
mathematical terms).
It's what you call "intersection", obviously.