摘要
外连接是多库系统中经常使用的生成全局视图的方法 ,但是外连接给维护多库系统视图带来了很大的困难 .目前已有的多库系统视图维护算法只考虑了连接操作 (select project join,SPJ) ,如果全局视图是通过外连接生成的 ,这些算法就不能有效地维护多库系统视图的正确性 .提出了一种新的多库系统视图维护算法 ,它能够在有外连接及数据不一致的情况下高效地维护多库系统视图 ,并最大限度地减少了向局部数据库发送的查询数 。
Outjoin is one of the most frequently used operations for creating global view in multidatabase, but it makes multidatabase'view maintenance more difficult. Most of the existing view maintenance algorithms only consider the views defined by select project join (SPJ) queries. Once the view is created by outjoin, those existing algorithms may fail in view maintenance. In this paper a new view maintenance algorithm is introduced, which can handle view involving outjoin, regular join, and data inconsistency. Moreover, the maintenance mechanism minimizes the number of the queries that need to be sent to the local database systems for view maintenance, which is an efficient way to make the multidatabase system more efficient.
出处
《计算机研究与发展》
EI
CSCD
北大核心
2000年第7期789-795,共7页
Journal of Computer Research and Development
基金
国家"八六三"高技术研究发展计划基金项目资助
关键词
视图维护
多库系统
外连接
数据模式
view maintenance, multidatabase, outjoin, dangling tuple
