This topic string USES the special wildcard + character, which enables Northern air to subscribe to arrivals for all airports.

此主题字符串使用了特殊的通配符+字符，它让Northern Air得以订阅所有机场的航班抵达信息。

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A subscriber (but not a publisher) can specify a topic name that contains wildcard characters, which creates a single subscription to multiple topics, such as a branch in a topic hierarchy.

订户(而非发布者)可以指定包含通配符的主题名称，这将创建订阅多个主题的单个订阅，如主题层次结构中的某个分支。

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The match may be exact if the publisher and subscriber specify exactly the same topic name, or the subscriber may specify a wildcard to match many different published topics.

如果发布方和订阅方指定的是完全相同的主题名称，则可能是精确匹配，否则订阅方可以指定通配符来匹配很多不同的发布主题。

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