Journal of Software:2000.11(12):1656-1659

(哈尔滨工业大学 计算机科学与工程系,黑龙江 哈尔滨,150001;燕山大学 计算机科学与技术系,河北 秦皇岛,066004;哈尔滨理工大学 计算机系,黑龙江,哈尔滨,150080)
Decomposition Condition and Algorithm of β-Acyclic in Mixed Dependency Environments Based on Line Graph
LIU Wen-yuan,HAO Zhong-xiao
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Received:May 18, 1999    Revised:September 20, 1999
> 中文摘要: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4NF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.这一结论可直接指导数据库的模式设计.
Abstract:β-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.
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LIU Wen-yuan,HAO Zhong-xiao.Decomposition Condition and Algorithm of β-Acyclic in Mixed Dependency Environments Based on Line Graph.Journal of Software,2000,11(12):1656-1659