| 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. |
| 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 |
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| Decomposition Condition and Algorithm of β-Acyclic in Mixed Dependency Environments Based on Line Graph |
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LIU Wen-yuan,HAO Zhong-xiao
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| 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. |
| Key words: database scheme mixed dependency line graph β-acyclic lossless join keep dependency |
