public function validatesInclusionOrExclusionOf($type, $attrs)
	{
		$configuration = array_merge(self::$DEFAULT_VALIDATION_OPTIONS, array('message' => Errors::$DEFAULT_ERROR_MESSAGES[$type], 'on' => 'save'));

		foreach ($attrs as $attr)
		{
			$options = array_merge($configuration, $attr);
			$attribute = $options[0];
			$var = $this->model->$attribute;

			if (isset($options['in']))
				$enum = $options['in'];
			elseif (isset($options['within']))
				$enum = $options['within'];

			if (!is_array($enum))
				array($enum);

			$message = str_replace('%s', $var, $options['message']);

			if ($this->isNullWithOption($var, $options) || $this->isBlankWithOption($var, $options))
				continue;

			if (('inclusion' == $type && !in_array($var, $enum)) || ('exclusion' == $type && in_array($var, $enum)))
				$this->record->add($attribute, $message);
		}
	}