一种适合多数据库系统的查询表示方法

An Approach of Query Representation for Query Processing in Multidatabase Systems

1 引言随着分布计算和网络技术的不断发展,传统的数据库技术已越来越不能满足数据共享和互操作的需要.同时,已有的数据库系统又不可能全部丢弃.因而研制能同时访问和处理来自多个数据库中数据的多数据库系统已成为必然趋势.多数据库系统是解决已存的、异构的、分布的多个局部数据库系统之间数据共享和集成的问题.由于多数据库系统具有异构性、分布性和局部自治性的特点,使得多数据库查询处理与传统数据库查询处理有很大的不同.

A multidatabase system gives users a global schema. A user must use global query language to query the multidatabase system. So,query transformation from global query to local queries must be needed and middle queries must be used during this transformation. This paper presents an approach of query representation for query processing in multidatabase systems and gives the properties of equivalent transformation of the query. An algebra foundation of middle class operations is also introduced to achieve the algebra optimization during the course of transformation from global query to middle queries.