public function concerns($names, array $options = [])
    {
        $names = (array)$names;
        
        foreach ($names as $name) {
            if (isset($this->concerns[$name])) {
                $this->concerns[$name]($this, $options);
            } else {
                throw new Exception\InvalidArgumentException(
                    sprintf("No concern named '%s' was found!", $name)
                );
            }
        }
    }