The three-layered architecture model partition the information system into the client present layer, application service layer and database layer.

该体系结构模型将系统划分为客户端表示层、应用服务层、数据层。

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In hybrid form, a private cloud can include data stored on premise or off, with a private Platform-as-a-Service middleware layer managing application data and enforcing data security.

FORBES: The Data Protection And Security Case For Private Clouds