关系模式算法设计

摘  要

数据库技术是计算机科学中发展最快的领域之1，也是应用最广的技术之1，它已成为计算机信息系统与应用系统的核心技术和重要基础。数据库设计是数据库应用系统设计的重要步骤,数据库是否适合应用系统的设计是至关重要的，为了使数据库设计方法走向完备，人们研究了规范化理论，主要通过讨论1个关系属性间不同的依赖情况，讨论如何根据属性间依赖情况来判定关系是否具有某些不合适的性质，关系数据中的关系是要满足1定要求的，满足不同程度要求的为不同范式。本文讨论的是给出1个范式，判定是那1种范式。 本文在函数依赖的范畴内对关系模型的规范化理论及其运用问题进行了探讨，对2NF,3NF,BCNF范式进行了研究，实现了上面3种范式的自动生成算法，简化了范式的判定难度。系统地提出1整套使用地关系规范化地具体方法和步骤，给出了1个判定关系模式是否属于其中1种的算法。根据本文提供的方法可以容易判断1个关系模式，从而避免了因为数据库设计不当而对数据库管理系统造成的影响。
关键字：函数依赖；候选关键字；闭包；传递依赖。

Abstract

The technology of the database is one of the fields with the fastest developing speed in computer science, using one of the widest technology too, it has already become information system of the computer and the key technology of the application system and important foundation. Data design of storehouse whether database use important step that system design, database suitable for design of application system essential, in order to make the database design method move towards being complete, people have studied the standardized theory, one relation different reliance situation under attribute through discussion, discuss how rely on situation is it judge according to attribute relation have some improper nature to come mainly, concern relation of data to meet certain demand ,meet demand in various degree different normal form. What this text discussed is to provide a normal form ,judge which is it Normal form.Within the category of function dependency，the theory and application of normalization of relation model are studied. a set of practically specific methods of relation normalization are systematically put forward. To the 2NF, 3NF,the type of BCNF carried on a research, carrying out a top is three kinds of calculate ways with automatically born modeltypes, simplified the model type to judge a difficulty. And a polynom ial time algorithm to decide whether a relation model is in them given. And provide a arithmetic of determinant a relation pattern is or not pertain to bcnf. Using the way of this artrcle we can easy judge a relation mode, accordingly avoid the influence of unsuitable designing database.

注释：不含源代码