【摘要】 XML管理系统的查询处理效率很大程度上取决于系统中XML数据的存储模式 .在用户查询已知或可预测的情况下 ,根据用户查询设计存储模式可以改善系统的查询处理效率 .该文介绍VXMLR系统存储模式的自适应调整机制 .根据历史查询信息 ,VXMLR系统对其存储模式进行自适应调整 ,从而提高查询处理效率 .其基本思路是 :首先根据历史查询 ,推导出适当的映射规则 ,得到XML文档在关系数据库中的存储模式 ;然后 ,在给定的空间约束下 ,根据历史查询使用背包问题求解算法选择关系表进行垂直分割或冗余存储相关数据 ,使查询所访问的无关数据尽可能少 .VXMLR系统提供四种存储模式调整策略 ,其中两种策略可以实现自适应的存储模式调整 .实验结果表明文中提出的方法是有效的 .更多还原

【Abstract】 The efficiency of an XML management system depends mainly on its storage schema. Designing storage schema based on users’ queries can improve its performance significantly. This paper introduces the technique of XML storage schema adaptation in the VXMLR system. Based on history queries, the VXMLR system automatically adjusts its storage schema for speeding up query processing. First, some appropriate mapping rules are derived from the history queries, and then initial storage schema is generated by using these mapping rules. Second, under given space constraint and with the history queries, some relational tables are selected for vertical partitioning or redundant storage so that these tables can be accessed as fast as possible. Four kinds of schema adaptation strategies are presented, in which two are used for automatic schema adaptation. Experimental results validate the practicability and effectiveness of our proposed approach.更多还原