public static function overlapLeftMerge($overlap, $attribute, $field)
    {
        $overlap   = explode('.', $overlap);
        $attribute = explode('.', $attribute);
        $field     = explode('.', $field);

        for ($i=0; $i<count($overlap); $i++) {
            $field[$i] = $attribute[$i];
        }
        return implode('.', $field);
    }