You can test if certain data is in a message, and only perform say a database retrieve operation if the data is missing.

您可以测试消息中是否包含特定的数据，如果数据丢失，则可以执行数据库检索操作。

youdao

For each case, print the operation result. The result should be rounded to 2 decimal places If and only if it is not an integer.

对于每一个测试用例，输出结果。（小数***）结果应四舍五入小数点后2位（当且仅当它不是一个整数------注意：如果结果不是小数就不要精确）。

youdao

It is shown that utilization of one channel is not disadvantageous over another with any conditions if and only if the first channel can simulate operation of the another.

结果表明当且仅当第一条通道可模拟另一条通道的操作时，则第一条通道在任何情况下比另一条通道都有优势。

youdao

He points out that only works when one party (or coalition) is in charge, whereas "in a system built around an administration and a bicameral Congress, everybody is part of the government - and the government only functions if there exists a certain baseline spirit of co-operation between the mutually indispensable parts".

BBC: Shame, embarrassment and Congress