{moved from my talk, as started here, for the reason that interested Wikimpdians may discuss, quotation start:}
You recently created Category:Swiss contemporary painters as a sub-category of both Category:20th-century Swiss painters and Category:21st-century Swiss painters. However I suspect that the the hierarchy is incorrect here, and that 20th- and 21st-century should be subcats of Contemporary. A person could be a contemporary of the 20th or the 21st without having to be both - but with the current hierarchy all contemporary painters are (indirectly) in both 20th- and 21st-century categories.
