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A mapping strategy for querying multiple object databases with a global object schema

机译:使用全局对象模式查询多个对象数据库的映射策略

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In a multidatabase system which consists of object databases, a global schema created by integrating schemes of the component databases provides a uniform interface and high level location transparency for the users to retrieve data. The mapping information between the global and component schemas is important for the global query processing. In this paper, a mapping strategy is presented. A mapping equation is defined to denote the mappings for attributes and object instances among a virtual class and its constituent classes. In addition, a mapping graph is used to describe the mapping equation. According to the mapping information, the mechanism to process global queries is introduced. One processing unit is responsible to decompose the global query into the subqueries against the component databases. Moreover, to handle the effects of schema restructuring, preprocessing and postprocessing units are provided for each local DBMS. Finally, the results returned from component databases need to be integrated. The certain result and maybe result for a global query are discussed. Also, the situation where a real-world entity is represented in different component databases as different objects is considered for the result integration.
机译:在由对象数据库组成的多数据库系统中,通过集成组件数据库的方案创建的全局模式为用户提供了统一的接口和高级位置透明度,以检索数据。全局和组件模式之间的映射信息对于全局查询处理很重要。在本文中,提出了一种映射策略。定义映射方程式以表示虚拟类和其成分类之间的属性和对象实例的映射。另外,映射图用于描述映射方程。根据映射信息,介绍了处理全局查询的机制。一个处理单元负责将全局查询分解为子查询,针对组件数据库。此外,为了处理模式重组的效果,为每个局部DBMS提供预处理和后处理单元。最后,需要集成从组件数据库返回的结果。讨论了某个结果,也许是结果的全局查询。此外,实际实体在不同的组件数据库中表示为不同对象的情况被认为是结果集成。

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