root.map(Activation::getFile).ifPresent(fa -> {
            stk.push(new ActivationFrame("file", Optional.of(fa)));
            stk.push(new ActivationFrame("exists", Optional.empty()));
            validator.accept(fa.getExists());
            stk.peek().location = "missing";
            validator.accept(fa.getMissing());
            stk.pop();
            stk.pop();
        });
        root.map(Activation::getOs).ifPresent(oa -> {