protected function update()
	{
		// New objects can't be updated, neither can frozen
		if ($this->is_new())
		{
			return false;
		}

		// Non changed objects don't have to be saved, but return true anyway (no reason to fail)
		if ( ! $this->is_changed(array_keys(static::properties())))
		{
			return true;
		}

		$this->observe('before_update');

		// Create the query and limit to primary key(s)
		$query       = Query::forge(get_called_class(), static::connection(true));
		$primary_key = static::primary_key();
		$properties  = array_keys(static::properties());
		//Add the primary keys to the where
		$this->add_primary_keys_to_where($query);

		// Set all current values
		foreach ($properties as $p)
		{
			if ( ! in_array($p, $primary_key) )
			{
				if (array_key_exists($p, $this->_original))
				{
					$this->{$p} !== $this->_original[$p] and $query->set($p, isset($this->_data[$p]) ? $this->_data[$p] : null);
				}
				else
				{
					array_key_exists($p, $this->_data) and $query->set($p, $this->_data[$p]);
				}
			}
		}

		// Return false when update fails
		if ( ! $query->update())
		{
			return false;
		}

		// update the original property on success
		$this->observe('after_update');

		return true;
	}