论文标题:面向对象数据库规范化理论中几个关键问题的研究
RESEARCHING ON SEVERAL KEY PROBLEMS ABOUT NOTMALIZATION THEORY FOR OBJECT-ORIENTED DATABASE
论文作者 郭洪禹
论文导师 刘国华,论文学位 硕士,论文专业 计算机应用技术
论文单位 燕山大学,点击次数 107,论文页数 100页File Size2951k
2001-01-01论文网 http://www.lw23.com/lunwen_168156682/ 面向对象数据库;规范化;用户解释;对象解释;依赖约束;范式; 冲突;最小覆盖;GD-约束
object-oriented database; normalization; user interpretation; object interpretation; dependency constraints; normal form; conflict; minimal cover; GD-constraint
面向对象规范化理论是Z.Tari等人1997年在文[1]中首次提出的。同传统的关系数据库规范化理论的最大区别是面向对象规范化理论主要用于数据库的概念设计，与数据库的逻辑设计无关。这弥补了传统的数据库设计方法在概念模式方面的不足，使其支持面向对象数据模型。面向对象数据库理论作为近年来兴起的理论，在很多方面还有待完善。 本文针对以下面向对象规范化理论中几个关键问题进行了分析研究，并提出了求解方法。 对象候选关键字不仅在关系数据规范化理论中处于重要位置，在面向对象规范化理论中也充当非常重要的角色，本文针对对象候选关键字的求解问题进行了探讨，找到了一种求解对象候选关键字的算法。 面向对象规范化过程是以全局依赖集提供的依赖约束为基础进行的，因此，全局依赖集的简化程度直接影响着规范化过程的效率。本文对最小覆盖求解问题进行了详细讨论，给出了一个时间复杂性为0（m~2）的求解算法。 含有冲突用户解释特征的研究。当对象的用户解释含有冲突时，对象将永远无法规范化为规范化对象，为建立规范化对象就必须识别含有冲突的用户解释。本文通过对含有冲突用户解释的研究，归纳出了用户解释含有冲突时的三个特征。 面向对象数据模型规范化算法的研究。对象规范化问题是面向对象规范化理论中的核心问题。本文对含有冲突用户解释进行了详细研究，提出了一种基于图的规范化算法。这一算法可识别含有冲突的用户解释，从而改进了文献[1]中提出的规范化算法。 通过对以上面向对象模型规范化理论中几个关键问题的研究，使得面向对象模型规范化理论更加完善。
Normalization theory for object-oriented database was first brought forward in literature [1] by Z.Tari etc. in 1997. In contrast to conventional normalization theory for relational database, the normalization theory for object-oriented database is mainly used for database conceptual design, and independent of database logical design. In this point, it makes up for the inadequacy in logical schema, and supports the object-oriented schemata. As prospering in recently years, the theory for object-oriented database has some inadequacy and is waiting to be perfected. This paper proposed several key problems about the normalization theory about object-oriented database, and provided related solutions. The problem about candidate key of an object is an important problem in normalization theory not only for relational database but also for object-oriented database. In this paper, the problem for finding a candidate key of object was studied in details and proposed an algorithm for finding a candidate key of object. The normalization process for object-oriented database is based on the set of dependency constraints provided by the set of global dependency. So, the reduced degree of the set of global dependency affects the efficient of normalization process directly. In this paper, the problem for finding a minimal cover of a set of GD-constraints is studied. Finally, an algorithm for finding a minimal cover of a set of GD-constraints with time complexity 0(m2) is proposed. The features of the user interpretation with conflicts were studied. Once there is the user interpretation with conflicts in object, the object will never be normalized into a normalization object. In this paper, three features of the user interpretation with conflicts are extracted by studied in details. Normalization algorithm for object-oriented data model is studied. The problem of normalization for object is the kernel problem in normalization theory for object-oriented database. In this paper, the user interpretation with conflicts was studied in details. Based on this, a normalization algorithm in terms of a directed graph was provided. This normalization algorithm can identify the user interpretation with conflicts, so it improves on algorithms cited in literature [1].IIAbstract Through the research on several key problems about normalization theory for object-oriented database , this paper makes some contributions towards the development of normalization theory for object-oriented data models.
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