无内部冲突数据库模式满足P3及无β环判定问题研究  

Research on Deciding a Database Schema Without Inside Conflicts Meeting P_3 and β-Acyclicity

作　　者：郝忠孝[1] 顾照鹏[1] 

机构地区：[1]哈尔滨理工大学计算机科学与技术学院

出　　处：《计算机研究与发展》2008年第6期1056-1063,共8页Journal of Computer Research and Development

基　　金：黑龙江省自然科学基金项目(F2006-01)~~

摘　　要：通过分析在FD集F的最小归并依赖集D无弱左部冲突、弱右部冲突时相邻归并依赖所具有的性质和特征,提出了左部集冲突、蕴含集间冲突和主归并依赖冲突等概念,在此基础上证明了在FD集F无内部冲突且最小归并依赖集D中存在弱左、右部冲突、左部集冲突、蕴含集间冲突和主归并依赖冲突时模式分解为满足P3为有β环的结论,并给出了左部集冲突、蕴含集间冲突和主归并依赖冲突的判定算法及分析,为进一步研究无β环的分解奠定了基础.The α-acyclic database eliminates several good properties such as the join dependency of R is equivalent to a set of multivalued dependencies and every pairwise consistent database over R is globally consistent. The α-acyclic database mainly concerns the acyclicity of global database schema, but there still exists cycles in subschemas. Expect α-acyclic database＇s merits β-acyclic database has acyclicity of subgraph, so β-acyclic database can effectively eliminate the abnormality of subschemas. Being a kind of important acyclic levels, the property of β-acyclicity has become basic demand in normalization with lossless join, keeping dependency and 3NF under FD environment. By analyzing the property and characteristics of two adjacent merge dependencies in D （the minimum merge dependency set of F） when D is without weak left side conflict and weak right side conflict, the definitions of left side set conflict, conflict between implicit sets and main merge dependency conflict are introduced. On this basis, the scheme decomposition is discussed and the result concludes that when D has weak left side conflict or weak right side conflict or left side set conflict or conflict between implicit sets or main merge dependency conflict, the decomposition meeting P3 is β-cyclic, and the algorithm and its analysis is presented, laying down the foundation for further investigation of β-acyclic decomposition.

关 键 词：无内部冲突 无Β环 模式分解 超图 线图 

分 类 号：TP311.13[自动化与计算机技术—计算机软件与理论]