无冲突满足P_4的无U环数据库模式分解条件的研究  

STUDY OF DATABASE SCHEMA DECOMPOSITION CONDITION OF CONFLICT FREE, MEETING P 4 AND β ACYCLIC

作　　者：刘文远[1,2] 郝忠孝[1,3] 

机构地区：[1]哈尔滨工业大学计算机科学与工程系 [2]秦皇岛066004 [3]哈尔滨150002

出　　处：《计算机研究与发展》2000年第2期170-174,共5页Journal of Computer Research and Development

摘　　要：无β环是一种重要的无环级别，与无损联接、保持依赖和４ＮＦ一起，成为多值依赖环境下数据库模式规范化的基本要求，能够直接指导数据库的模式设计．文中提出了严格无冲突的概念，以线图为工具，证明了应用分解树算法对一个严格无冲突的ＭＶＤ集分解得到的数据库模式对应的线图及等权化简子图都是三角化的，而且线图中每个三角形都是相容的．最后得出无冲突条件下无β环且满足保持数据依赖、无损联接和４ＮＦ的数据库模式分解的充要条件是给定的ＭＶＤ集存在一个严格无冲突的覆盖．Being a kind of important acyclic degrees, β acyclic has become basic demand of normalization with lossless join, keep dependency and 4NF under MVD environment, and can guide directly database schema design. In this paper, the concept of strictly conflict free is given, and using the line graph as tools, it is certified that line graph of a database schema and its duplicate reduced sub graph are triangulated, and every triangle in line graph is compatible. Database schema is decomposed from a strictly conflict free MVD set by using a decomposition trees algorithm. It is concluded that the sufficient and necessary condition of database schema decomposition satisfying lossless join, keep dependency, 4NF, and β acyclic under conflict\|free condition is that the MVD sets have a strictly conflict free cover.

关 键 词：数据库模式 设计 无冲突 无β 

分 类 号：TP311.13[自动化与计算机技术—计算机软件与理论]