图1说明了这种三层应用程序模型。

Figure 1 illustrates the three-tiered application model.

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三层应用程序开发已经成为流行的开发方法，美国微软公司最新的。

Three-Tier application and development is more and more popular, and Microsoft.

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以三层应用程序为例，如果将数据库放在云中，而将另外两层留在企业内部，就成问题。

With a three-layer application, it would be problematic to, for instance, put the database in the cloud and keep the other two layers on-site.

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