发布者和订户通过主题相关，而主题表示订户该兴趣的数据类别。

The publisher and subscribers are related by a topic, which represents the category of data in which the subscribers are interested.

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数据类别类似于抽象基类，比如，一个类别可以表示所有的汽车型号。

Data categories are like abstract base classes; a category might be able to represent all models of car, for instance.

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数据类别可以包含几个数据项，这些数据项链接到您此前创建的配置项。

Data categories can contain a number of data items, which are linked to the profile items you created earlier on.

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