Because a kind of basic mismatch exists between object model and relation model, it leads to that object systematic developer spend a large amount of time taking object persistent.

由于对象模型和关系模型之间存在一种基本的阻抗不匹配，导致使用关系数据库的面向对象系统开发人员通常要花费大量的时间来将对象持久化。

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The author of this paper has researched into the concept and character of space object, the relation between space object and space debris, and the relation between space object and aerospace objects.

对空间物体的概念、特征进行了研究，探讨了空间物体与空间碎片以及航空航天物体之间的关系，从而明确了空间物体的内涵与外延。

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The Mapping process each element in DTD and mapping to an object schema. Then the object schema is mapped to the relation database schema.

映射的策略是以分析处理DTD中的每一个元素映射为对象模型，再由对象模型映射为数据库的关系模型。

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