该模型分为五个层，即：环境支持层、运行平台支持层、物理管理层、映射层和应用层，并具体讨论了每一层的功能和开发方法。

The model consists of five layers which are environment support layer, running platform support layer, physical management layer, mapping layer, and application layer.

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由于本系统只限于应用层程序的探讨，所以对具体的压缩算法不做深究。

Because this system is limited to application layer discussion, so do go into the specific compression algorithm.

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