function add($type, $id, $field, $amount = 1)
	{
		$this->init($type, $id);
		if(!isset($this->data[$type][$id]['add'][$field]))
		{
			$this->data[$type][$id]['add'][$field] = 0;
		}
		$this->data[$type][$id]['add'][$field] += $amount;
	}