我们将前两层称为高级服务层和低级服务层。

We'll refer to the first two layers as high-level and low-level service layers.

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与前两层的情况相反，数据库层的规模评估相当容易。

In contrast, sizing the database layer is relatively easy.

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前两层主要对输入信息进行预处理和特征提取，第三层主要对特征信息进行全局决策。

The first two layers primarily handle in advance and abstract the input information. The last layer makes the whole decision for the information with features.

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