public static function getNumberOperands($includeSelector = false)
    {
        $values = array(
            self::OPERATOR_EQUAL,
            self::OPERATOR_GREATER_THAN,
            self::OPERATOR_GREATER_THAN_EQUAL,
            self::OPERATOR_LOWER_THAN,
            self::OPERATOR_LOWER_THAN_EQUAL,
        );

        if ($includeSelector) {
            $values[] = self::OPERAND_SELECTOR;
        }

        return $values;
    }