一种实现数据集成中查询重写的方法

Approach to query reformulation in data integration

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 .

In order to make attributes of entities consistent in every subquery, a concept of mapping dependence is proposed in terms of the path mapping between schemata, and a method of reformulation is given. By this method, when traversing each node of query tree in reformulation, the system holds a PC-context for every temporary result reformulated, and in terms of heuristic rules judges whether or not the PC-context and the dependence of current mapping are consistent. The time complexity of algorithm in this method is linear with the size of data sources.