在参与分布式查询的所有数据库中，各种数据类型必须定义有相同的层次结构和类型转换。
The distinct data types must have exactly the same hierarchy and casts defined in all databases participating in the distributed queries.
保存动态、分布式、层次的和有状态信息要求一个不同的基础设施，它不是以关系数据库为中心的。
Storing stateful information that is dynamic, distributed and hierarchical requires a different infrastructure that is not relational database centric.
分布式多层系统由客户端应用程序，应用程序服务器和数据库服务器层次构成。
Distributed-tier structure is included to Client application program application program sever and Database sever.
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