protected function _operator($model, $key, $op, $value, $schema) {
		$castOpts = compact('schema') + array('first' => true, 'arrays' => false);

		switch (true) {
			case !isset($this->_operators[$op]):
				return array($op => $this->cast($model, array($key => $value), $castOpts));
			case is_callable($this->_operators[$op]):
				return $this->_operators[$op]($key, $value);
			case is_array($this->_operators[$op]):
				$format = (is_array($value)) ? 'multiple' : 'single';
				$operator = $this->_operators[$op][$format];
			break;
			default:
				$operator = $this->_operators[$op];
			break;
		}
		return array($operator => $value);
	}