数据库模式在FD环境下满足P_s及无α环判定问题

Deciding Problem of Database Schema Meeting P_s and α-acyclic in Functional Dependency

通过分析在FD集F的最小归并依赖集D存在弱左部或弱右部冲突时所具有的性质和特征,提出了Ps(保持FD,无损连接且满足SNF)、条件T等概念。在此基础上讨论了数据库模式分解为SNF的无α环判定问题,给出了在D有弱左部或弱右部冲突及不满足条件T时满足Ps的分解是有α环的结论,为进一步研究无α环的分解奠定了基础。

By analyzing the properly and characteristics of D（ the minimum merge dependency set of F） when D has weak left side conflict or weak left side conflict, the notions of Ps（join-lossless, FD and SNF）, condition T are introduced. On this basis, the scheme decomposition is discussed and the result concludes that when D has weak left side conflicts or weak right side conflict or doesn＇t meet condition T, the decomposition meeting P, is α-cyclic, laying the foundation for further investigation of α-acyclic decomposition.