一种实现数据集成中查询重写的方法

基于路径映射的XML数据集成系统在查询重写时可能会生成不合理的子查询. 为了让生成的各个子查询中的实体属性是一致的,按照模式之间的路径映射提出了映射依赖的概念,并设计了一种查询重写的方法.重写时依次遍历查询树的各个结点,记录每个中间结果的PC环境,根据启发式规则判断PC环境与当前映射的依赖是否保持一致.并且在时间复杂度上该方法和数据源的数目成线性关系.

Approach to query reformulation in data integration

In order to make attributes of entities consistent in every subquery, a concept of mapping dependence is proposed in terms of the path mappings between schemas, and a method of refor mulation is designed. By this method, when traversing each nodes of query tree i n reformulation, system holds a PC context for every temporary result reformula ted, and in terms of heuristic rules judges whether or not the PC context and t he dependence of current mapping selected are consistent. The time complexity o f algorithm in this method is linear with the size of data sources.