RE: [External] : Re: [PATCH v3] Allow applying filters to summary consecutively

[Drew Adams]

> 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).

I didn't realize that's what this is about.

If so, it's not "filtering".  Filtering
_subtracts_ from the input set - it filters
out zero or more members.  Filtering can't
_add_ to the input set.

A filter is a sieve: "a device that removes
something from whatever passes through it".

https://www.wordwebonline.com/search.pl?w=filter

If you have an operation that starts with a
(possibly empty) set and lets you add to it,
that can't reasonably be called "filtering".

For what I think you're describing, I use
the verbs "narrow" (for filtering - set
intersection) and "widen" (for set union).

In terms of predicates / Boolean, it's
AND (multiplication) and OR (addition),
respectively.