基于线图的无β环混合依赖分解条件及算法  

Decomposition Condition and Algorithm of β-Acyclic in Mixed Dependency Environments Based on Line Graph

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,黑龙江哈尔滨150001 [2]燕山大学计算机科学与技术系 [3]哈尔滨理工大学计算机系

出　　处：《软件学报》2000年第12期1656-1659,共4页Journal of Software

摘　　要：无β环数据库模式具有很多优良的特性 ,以往的研究都局限在图论的范畴内 ,而没有考虑数据库的其他规范化特性 .在混合依赖基概念的基础上 ,定义了严格无冲突、扩展严格无冲突等概念 ,并证明了在混合环境下得出的无损联接、保持依赖、无 β环且满足 4 N F的分解的充要条件是 ,混合依赖集是扩展严格无冲突的 .据此 ,给出了判断严格无冲突及混合环境下无β环分解算法 ,并分析了算法时间的复杂度是线性的 .最后 ,给出基于线图的实例验证 .Acyclic database scheme has a number of desirable properties, but most former researches about β acyclic are based on graph theory, without consideration on other canonical properties of database. With the concept of mixed dependency basis, this paper defines the concepts of strict conflict free and extended strict conflict free, and proves that decomposition satisfies lossless join, keeps dependency, β acyclic and 4NF if and only if it is extended strict conflict free in the mixed environment. Based on this, the paper gives the algorithm for judging strict conflict free and β acyclic decomposition in mixed environment, then shows that the complexity of the algorithm is linear using an example based on line graph. This conclusion can directly guide real database designing.

关 键 词：数据库模式 混合依赖 线图 无Β环 无损联接 保持依赖 

分 类 号：TP311.13[自动化与计算机技术—计算机软件与理论]