为了实现第二种方法，需要在初次约会表单中捕捉附加的信息。
To implement this second approach requires additional information to be captured in the initial appointment form.
该方法实现简单，但存在缺陷：由于附加块信息不同于正常通信过程，恶意用户容易察觉通信具有密钥恢复功能，使用数据包过滤方法，就可以完全屏蔽密钥恢复功能。
The implementation is practical but with obvious disadvantage: the illegal user can easily notice the key recovery, and by data package filtering, the key recovery function can be screened.
以往在数据立方体上实现的联机聚集往往需要附加空间来存储联机聚集估算所需要的信息，极大地影响了数据立方体的存储和维护性能。
Typically, online aggregation algorithms on multi-dimensional data need additional auxiliary data for estimation, which make the performance of the storage and maintenance of the data cube worse.
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