空值环境下关系数据库查询处理方法

本文给出了一种处理占位型空值的简化方法，解决了空值环境下关系数据库的查询问题，针对不同的空值语义语义特点和查询中的作用，定义了三种不同的操作。ＤＥＦＩＮＩＴＥ，ＥＸＩＳＴ，ＭＡＹＢＥ。同时，给出了含有这三种操作的选择运算、集合差、一般连接运算的新定义。     

ESTIMATING NULL VALUES IN RELATIONAL DATABASE SYSTEMS HAVING NEGATIVE DEPENDENCY RELATIONSHIPS BETWEEN ATTRIBUTES

Ontologies are widely considered to be the backbone of the Semantic Web. Its importance is being recognized in a multiplicity of research fields and application areas. Ontology building is crucial for the aforementioned issues. The main goal of this research is to investigate an effective methodology for collaborative ontology building. A trust-based consensus is proposed to support an efficient solution for conflicts among different viewpoints of participants in the collaborative ontology (CoO) building process. In every cycle of the iterative collaborative process, the ontology is refined and evolved by reaching a trust-based consensus among the participants’ viewpoints. The proposed method is applied for collaborative Vietnamese WordNet building. The result is significant in comparison with previous approaches.     

GENERATING FUZZY RULES FROM RELATIONAL DATABASE SYSTEMS FOR ESTIMATING NULL VALUES

This paper presents a new algorithm for constructing fuzzy decision trees from relational database systems and generating fuzzy rules from the constructed fuzzy decision trees. We also present a method for dealing with the completeness of the constructed fuzzy decision trees. Based on the generated fuzzyrules, we also present a method for estimating null values in relational database systems. The proposed methods provide a useful way to estimate null values in relational database systems.     

GENERATING AUTOMATIC FUZZY SYSTEM FROM RELATIONAL DATABASE SYSTEM FOR ESTIMATING NULL VALUES

There are many methods trying to do relational database estimations with a highly estimated accuracy rate by constructing a fuzzy learning algorithm automatically. However, there exists a conflict between the degree of the interpretability and the accuracy of the approximation in a general fuzzy system. Thus, how to make the best compromise between the accuracy of the approximation and the degree of the interpretability is a significant study of the subject. In order to achieve the best compromise, this article attempts to propose a simple fuzzy learning algorithm to get a positive result in the relational database estimation on the real world database system, including partition determination, automatic membership function, and rule generation, and system approximation.     

A NEW METHOD TO GENERATE FUZZY RULES FROM RELATIONAL DATABASE SYSTEMS FOR ESTIMATING NULL VALUES

Fuzzy decision trees can be used to generate fuzzy rules from training instances to deal with forecasting and classification problems. We propose a new method to construct fuzzy decision trees from relational database systems and to generate fuzzy rules from the constructed fuzzy decision trees for estimating null values, where the weights of attributes are used to derive the values of certainty factors of the generated fuzzy rules. We use the concept of "coefficient of determination" of the statistics to derive the weights of the attributes in relational database systems and use the normalized weights of the attributes to derive the values of certainty factors of the generated fuzzy rules. Furthermore, we also use regression equations of the statistics to construct a complete fuzzy decision tree for generating better fuzzy rules. The proposed method obtains a higher average estimated accuracy rate than the existing methods for estimating null values in relational database systems.     

含有空值关系数据库的查询处理

本文在深刻理解空值语义的基础上，给出一种处理占位型空值的方法，空值环境下关系数据库的查询策略，定义了含三种查询操作的关系代数最小完备集中的关系代数运算，并对查询计算的有效性和完备性进行了分析。     

含空值关系数据库中关系代数的实现

本文从空值的完全语义出发，依据空值环境下信息等价和信息相容的含义，全面定义了空值环境下运算结果完备的关系代数运算，并对空值环境下关系代数运算的有效性和完备性进行了讨论。     

关系数据库中的知识发现研究

本文提出了一种关系数据库中的知识发规模型;介绍了相关的机器学习、关系数据库、模糊学和统计学等技术;分析了现有的一些系统;最后,讨论了进一步研究的问题。     

关系数据库中的模糊知识发现

本文提出用部分量词和模糊谓词来表示模糊知识这一方法，在简要介绍数据抽象这一关系数据库中知识发现的方法后，详细描述了该方法中对模糊性问题的处理方法．     

关系数据库的证据生成与合成

本文在加上引进了关系分划，利用外延空间上的概率分布得到了证据的信任函数，并给出了证据合成的Ｄｅｍｐｓｔｅｒ－Ｓｈａｆｅｒ公式的简化计算方法及在专家系统中的应用。     

分布环境下的工程更改管理

通过分析工程更改的业务流程，总结出其工作特点，提出工程更改采用基于MBOM的分布管理模式。     

LEARNING IN RELATIONAL DATABASES: A ROUGH SET APPROACH

Knowledge discovery in databases, or dala mining, is an important direction in the development of data and knowledge-based systems. Because of the huge amount of data stored in large numbers of existing databases, and because the amount of data generated in electronic forms is growing rapidly, it is necessary to develop efficient methods to extract knowledge from databases. An attribute-oriented rough set approach has been developed for knowledge discovery in databases. The method integrates machine-learning paradigm, especially learning-from-examples techniques, with rough set techniques. An attribute-oriented concept tree ascension technique is first applied in generalization, which substantially reduces the computational complexity of database learning processes. Then the cause-effect relationship among the attributes in the database is analyzed using rough set techniques, and the unimportant or irrelevant attributes are eliminated. Thus concise and strong rules with little or no redundant information can be learned efficiently. Our study shows that attribute-oriented induction combined with rough set theory provide an efficient and effective mechanism for knowledge discovery in database systems.     

映射对象到关系数据库

面向对象技术是当今最流行的软件开发方法,关系模型是最常用的一种数据模型。如何用关系数据库实现持久对象的存储成为信息系统成功的关键。本文对映射对象模型到存储数据的关系模型的方法进行了探讨。     

ESTIMATING DBLEARN'S POTENTIAL FOR KNOWLEDGE DISCOVERY IN DATABASES

We propose a procedure for estimating DBLEARN's potential for knowledge discovery, given a relational database and concept hierarchies. This procedure is most useful for evaluating alternative concept hierarchies for the same database. The DBLEARN knowledge discovery program uses an attribute-oriented inductive-inference method to discover potentially significant high-level relationships in a database. A concept forest, with at most one concept hierarchy for each attribute, defines the possible generalizations that DBLEARN can make for a database. The potential for discovery in a database is estimated by examining the complexity of the corresponding concept forest. Two heuristic measures are defined based on the number, depth, and height of the interior nodes. Higher values for these measures indicate more complex concept forests and arguably more potential for discovery. Experimental results using a variety of concept forests and four commercial databases show that in practice both measures permit quite reliable decisions to be made; thus, the simplest may be most appropriate.     

分布式数据库中的限定关系代数变换

限定关系代数可用于分布式数据库操作符树的简化。本文详细讨论了限定关系代数变换的规划，并对前人的结论作了分析和改进。     

网络环境下异构数据库交互访问中数据格式转换的研究

随着企业间合作的增加以及电子商务的普遍开展,对建立异构数据库交互访问的需求日益迫切。本文讨论的是异构数据库问题的一个方面,即异构数据库交互访问中数据转换问题。本文分析了传统异构数据库交互中存在的问题,并探讨了利用XML实现异构数据库交互访问中数据转换的可行性,并进行了系统建模。     

分布式数据库数据分布模型的启发式算法

本文提出了以最小代价为目标的分布式数据库数据分布模型求解的启发式算法，利用数据分布的启发信息，将互相有紧密联系的ｎ个关系的数据分布问题分解为具有较松散联系的ｎ个关系的分布问题，并进行迭代调整，使算法的时间复杂度大为降低，算法精度也接近优化程度。     

分布式数据库研究的新方向

分布式数据库的研究已有二十余年历史。近年来半向何方发展 数据库的异构性与自治性,网络规模的膨胀以及移动计算技术的出现,都对分布式数据库技术提出新的挑战,本文从网络数据库的组织、等两个方面入手,讨论了分布式数据库研究所面临的几个新课题,最后对未来分布式数据库的发展前景作了展望。     

分布式环境下的关系型XML查询优化

XML数据查询是XML相关技术中一项的重要技术.与普通的XML查询方法不同,关系型XML查询不需要路径表达式,给查询者带来了便利,然而与此同时也带来了计算量增大的问题.针对该问题,给出了一种在分布式环境下基于部分求值的解决方案,并提出了优化算法.实验表明,该算法不仅能提高关系型XML查询的效率,而且能提高查询的适应性,使得查询可以在更为苛刻的条件下进行.