Planet RDF聚集部分的代码相对比较简单，依次注册清单中的每一个rss提要，获取每个RSS条目的键值，并保存所有条目的变化。

The aggregation part of the Planet RDF code is relatively simple: it regularly polls each RSS feed in the list, derives a unique key for an RSS item, and stores changes to each item.

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内容列表对负载进行解析，并使用键值与存储搜索标准进行比较。

The content list parses the payload and USES the key values to compare with the stored search criteria.

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关联谓词通常将事件中的某个键值(例如唯一旅行标识符)与包含相同键的度量作比较。

Correlation predicates typically compare some key value in the event, such as a unique trip identifier, with a metric containing the same key.

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