They are required to map between the different formats when the data flows from the service interface down to the database and back.

当数据在服务接口与数据库之间来回流动时，需要用这些操作来完成不同格式之间的映射。

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The data exposed on the service interface comes from the underlying database via the application code.

这个服务接口公开的数据是通过应用程序代码从底层数据库获得的。

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Listing 1 gives a simple example of a service interface, and a root data model class.

清单1给出了一个服务接口和根数据模型类的简单例子。

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The safest option is to store your data off-site, and Mozy offers that very service all wrapped in a user-friendly interface.

BBC: Weebly website