支持两种类型的查询：事件解决方案查询（它们只返回事件）和回答解决方案查询（它们可以返回任何非事件数据或聚合的结果）。
The two kinds of queries that are supported are: event solution queries, which return only events and the answer solution queries, which can return any non-event data or aggregated results.
元数据类型是特定内容类型与基础类型聚合的类型，提供特定于某类内容的特定属性。
Metadata types are those that specific content types aggregate with the base types to provide specific, well-known properties that are specific to a type of content.
系统为不同的数据类型提供了预定义的聚合函数。
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