Proposed Initiative - Extend WAC specification with triple-level filtering

[justinwb]

Creating this as a standalone initiative proposal from #72 so that it can be tracked individually. The UCR work should help to inform the scope, priority, and mission of this initiative.

[bblfish]

I'd just note that that seems like it may not be an easy thing to do correctly. I would say that could be a thing to add to a list of open research problems.