摘要
数据库设计的一个重要环节是将E-R模型转换为关系模型,但传统的E-R模型向关系模型的转换规则中存在一定的缺陷,在将具有时变性的多对多联系转换为关系后会导致关系的键无效。对导致转换后关系键无效的问题进行了深入分析,将问题根源归因为实体型间联系的时间性变化。在传统E-R模型引入联系的时变性质,据此将联系划分为动态联系和静态联系。提出了基于联系时变状态的新的E-R模型向关系模型的转换规则,修正了传统转换规则中的缺陷并解决了转换后的关系键失效问题。
The translating of Entity-Relationship model into Relational Data model is an important process of a database design. There are some defects in the traditional rules of translating, and these errors usually lead to a problem（called invalid-key） in a relation sche- ma coming fi＇om the Translating. This paper provides an exhaustive analysis of the problem, and shows that time-varying of relation- ship is the main reason which causes an invalid-key problem. This paper develops a new property for relationship, called state, and di- vides relationship into dynamic and statiC. This paper presents new rules of translating. It eliminates the defects in traditional rules, and solves the invalid-key problem.
出处
《计算机工程与应用》
CSCD
2012年第9期94-97,共4页
Computer Engineering and Applications
