The communication protocol is designed in term of three layers: Physical layer, Media Access Control layer and Logic Link Control layer.

本通信协议分为物理层、介质访问控制层和逻辑链路控制层三层设计。

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Of course, you can extend this behavior to access a database, perform complex business logic, or do anything else you might come up with to figure out what file to link to.

当然，您可以扩展这种行为，以访问一个数据库、执行复杂的业务逻辑或您想到的其他任何东西，从而判断出要链接的文件。

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The same logic also seems to fit naturally with how people link concepts together, often on the basis of loose associations and blurred boundaries.

同样的逻辑似乎也很自然的符合人类如何联系不同的概念，而这些概念都只有松散的联系和模糊的边界。

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Google's servers use similar logic, ranking Web sites according to how many other sites link to them and how lofty the referring sites are in the ranking.

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