public function setId( $key )
	{
		if( $key !== null )
		{
			$this->setCode($key);
			$this->_values['id'] = $this->_values['code'];
			$this->_modified = false;
		}
		else
		{
			$this->_values['id'] = null;
			$this->_modified = true;
		}
	}