概念格的内涵缩减与数据库推理依赖

值依赖是数据库推理问题研究的一个新课题.首先介绍了形式背景和概念格,提出了值依赖的形式概念模型.将数据属性的安全敏感级别引入到值依赖研究中,提出推理依赖及α极大推理依赖概念,并建立了形式概念格的内涵缩减与数据库推理依赖之间的关系.进一步证明了由概念格的内涵缩减推导出数据库中完备的、无冗余的α极大推理依赖集.最后提出并实例验证了发现数据库中全部推理依赖集的算法.推理依赖是关系数据库中最重要的属性依赖关系之一,其研究对检测和消除数据库推理通道具有十分重要的意义.     

基于Rough Set理论发现最小归纳依赖关系的方法研究

归纳依赖关系是数据库研究领域的重要概念,在数据库中自动发现最小归纳依赖关系对数据采掘具有重大意义。介绍了归纳依赖关系的概念、原理及利用Ｒｏｕｇｈ Ｓｅｔ理论度量数据属性间归纳依赖强度的方法,提出了一个在数据库中自动发现最小归纳依赖关系的算法。     

关系型数据库中的归纳依赖关系

数据依赖是数据库的一个重要概念,函数依赖则是一种常见的依赖关系。本文主要沦述另一种对     

一种用户任务级别上的数据库入侵检测方法

通常，更新数据库中一个数据项之前可能读或者写一些数据项，更新一个数据项后，可能也有一些数据项被更新。依据数据之间的这种依赖关系，本文提出一种用户任务级别 的数据依赖挖掘算法，从数据库日志中挖掘出用户任务事务中存在的数据依赖关系。如果在检测阶段发现同一用户任务中有事务与挖掘出的数据依赖关系不符合，则可判断此
此用户任务中有异常活动出现。     

基于JDBC的数据库连接池高效管理策略

在基于JDBC的数据库应用开发中,数据库连接的管理是一个难点,因为它是决定该应用性能的一个重要因素。论文在对数据库连接进行分析的基础上,提出并实现了一个基于连接池的高效管理策略,使得开发高性能的数据库应用变得相对容易。并对于连接管理中的两个难点:事务和多线程问题进行了剖析,给出了一个基于设计模式的解决方案及其实现原型。     

工程数据库版本管理的类引用和环境

ＣＩＭＳ要求工程数据库除了具备普通事务数据库的功能外，还应具有为适应工程设计环境所必须具备的特殊功能，其中包括要求工程数据库具备管理设计过程中对象演变历史的能力．因此，这就要求对设计的各个阶段形成同一工程实体的不同设计版本迸行版本管理．因而，如何维护对象的所有版本以支持动态引用成为一个重要的研究课题．本文针对该问题，介绍了实施类引用和环境（ｇｅｎｅｒｉｃｒｅｆｅｒｅｎｃｅｓａｎｄｅｎｖｉｒｏｎｍｅｎｔ）技术的目的，还就如何实施予以举例．     

全序时态候选关键字问题初步研究

与时间相关的数据库应用需求的不断增长,使得时态数据库设计成为非常重要的问题.在数据库的设计中,要充分考虑对数据依赖的处理.数据依赖是数据库设计理论中的一个核心概念,通过它可以规范属性之间满足的固有的语义约束.为了更有效的研究时态数据库中各种依赖以及各属性之间的关系,以便将进一步规范化,本文提出了全序时态左部属性、全序时...     

数据依赖与数据库规范化

任何一个数据库都会存在不同程度的数据冗余和更新异常等问题,为从源头上减少数据库的数据冗余和更新异常等问题,在数据库的设计过程中应进行规范化。通过对数据依赖和规范化理论进行研究,比较二者之间的关系来说明数据库的规范化过程,并以实例来分析规范化过程。分析比较发现规范化过程的实质是消除不合理的数据依赖。     

一个关系数据库可视查询系统的设计

本文讨论一个关系数据库的可视查询系统的设计。此系统为用户提供了一个新型交互式的数据库查询方式。它是一个在Unix操作系统环境下的位于数据库Db++和PERQ机的窗口管理系统间的软件。此系统可被用来在计算机显示屏幕上直接用“鼠标”构造与关系数据库内的关系相对应的可视图型,并对之进行数据库查询,从而大大地减低了人们对键盘的依赖,使广大终端用户能清楚,简便地了解数据库内的逻辑结构,提高了操作效率。     

空值环境下的完全函数依赖和部分依赖

本文给出了空值环境下的完全函数依赖的弱保持、强保持及部分函数依赖。提出并证明了不完全关系模式若不满足空值环境下的完全函数依赖的弱保持,则它的任意一个完备一定不是非空值环境下的完全函数依赖;若满足空值环境下的完全函数依赖强保持,则它的任意一个完备,一定是非空值环境下的完全函数依赖。本文还给出了判别不完全关系满足空值环境下的完全函数依赖强、弱保持的算法。为空值环境下的模式分解奠定了基础。     

A Logical Design Method for Relational Databases Based on Generalization and Aggregation Semantics

In this paper,a series of esign methods for relational databases based on generalization and aggregation semantics is set up.The relationship between a class and its subclass s considered as a scheme constraint.The concept of inheritance dependencies,which describes the multiple inheritance among schemes, is presented in the paper.It is shown that the inference rules for inheritance dependencies are sound and complete.Furthermore,a series of results about the closure of inheritance dependencies and the minimal set of inheritance dependencies,which are analogues to functional dependencies,is obtained.In order to describe the aggregation semantices,the concept of aggregation dependencies is given.It is easy to implement these constraints under relational database management systems.     

XML函数依赖研究综述

函数依赖作为数据库规范化的基础在关系理论中起着重要的作用。近年来，XML得到广泛应用并已成为互联网上数据传输和交换的标准。由于XML半结构化的特性，使得如何定义XML函数依赖使其具有更强的描述能力，以及如何解决相应的逻辑蕴涵问题成为当今学术界所面临的挑战。针对这些问题，系统地描述了目前关于XML函数依赖的研究现状，特别是把分析的重点放在如何定义函数依赖、判断其蕴涵关系以及从XML文档中发现函数依赖等问题上。最后讨论了诸如类型化函数依赖关系等一些相关的研究方向。     

XML模式中隐式冗余不存在的充要条件

XML数据库模式规范化设计是产生一组相关联的、能表示数据间依赖关系、而且消除了冗余的XML模式或DTD,以更好地进行信息检索.XML数据库模式中某些数据依赖的存在是冗余存在的原因,因此在XML数据库模式中数据依赖与冗余的关联是其规范化设计研究的关键问题,但对这一问题目前还没有专门的研究.XML数据库模式的数据依赖包括属性间数据依赖和元素间的数据依赖,给出综合了属性间和元素间数据依赖的XML数据库模式数据依赖的定义,分析与之关联的隐式冗余,并论证XML模式中隐式冗余不存在当且仅当该XML模式是规范的,为XML数据库模式规范化设计更深一层的研究奠定理论基础.     

Exploring into programs for the recovery of data dependenciesdesigned

Data dependencies play an important role in the design of a database. Many legacy database applications have been developed on old generation database management systems and conventional file systems. As a result, most of the data dependencies in legacy databases are not enforced in the database management systems. As such, they are not explicitly defined in database schema and are enforced in the transactions, which update the databases. It is very difficult and time consuming to find out the designed data dependencies manually during the maintenance and reengineering of database applications. In software engineering, program analysis has long been developed and proven as a useful aid in many areas. With the use of program analysis, this paper proposes a novel approach for the recovery of common data dependencies, i.e., functional dependencies, key constraints, inclusion dependencies, referential constraints, and sum dependencies, designed in a database from the behavior of transactions, which update the database. The approach is based on detecting program path patterns for implementing most commonly used methods to enforce these data dependencies     

Discovering interesting inclusion dependencies: application to logical database tuning

Inclusion dependencies together with functional dependencies form the most important data dependencies used in practice. Inclusion dependencies are important for various database applications such as database design and maintenance, semantic query optimization and efficient view maintenance of data warehouse. Existing approaches for discovering inclusion dependencies consist in producing the whole set of inclusion dependencies holding in a database, leaving the task of selecting the interesting ones to an expert user.In this paper, we take another look at the problem of discovering inclusion dependencies. We exploit the logical navigation, inherently available in relational databases through workloads of SQL statements, as a guess to automatically find out only interesting inclusion dependencies. This assumption leads us to devise a tractable algorithm for discovering interesting inclusion dependencies. Within this framework, approximate dependencies, i.e. inclusion dependencies which almost hold, are also considered.As an example, we present a novel application, namely self-tuning the logical database design, where the discovered inclusion dependencies can be used effectively.     

An analysis of multivalued and join dependencies based on the entity-relationship approach

In this paper, we show that multivalued dependencies and join dependencies are not very viable for certain cases of relational database design; they are sometimes difficult to be identified; they are relation sensitive; and we are unable to talk about these types of dependencies without referring to some specific relation. We also show that the entity-relationship approach can be used for relational database design without any of the above mentioned undesirable properties of multivalued dependencies and join dependencies.     

强偏序时态模式中数据依赖推导规则研究

随着数据库与信息技术的发展,信息系统面临许多新的应用和需求,对时态信息处理的需求越来越迫切。时态信息处理已成为许多新一代数据库与信息系统的关键技术,时态数据库研究已经成为数据库与信息系统领域研究的热点和难点。就时态数据库中的难点问题强偏序时态数据库的数据依赖问题开展研究,因此选题紧靠学术前沿。针对强偏序时态模式中的数据依赖问题进行了讨论,?提出了强偏序时态模块模式、强偏序模式的时态类型集概念,?给出了强偏序时态模式中函数依赖的推导规则以及多值依赖的推导规则,理论分析的结果表明这些规则是正确的有效的,这对实现强偏序时态数据库的规范化设计具有重要的推动作用。     

The integrity constraints for similarity-based fuzzy relational databases

This paper first introduces a new definition for the conformance of tuples existing in a similarity-based fuzzy database relation. Then the formal definitions of fuzzy functional and multivalued dependencies are given on the basis of the conformance values presented here. These dependencies are defined to represent relationships between domains of the same relation that exist. The definitions of the fuzzy dependencies presented in this study allow a sound and complete set of inference rules. In this paper, we include examples to demonstrate how the integrity constraints imposed by these dependencies are enforced whenever a tuple is to be inserted or to be modified in a fuzzy database relation. © 1998 John Wiley & Sons, Inc.     

样本依赖与连接依赖的等价性

以抽象代数为工具,探索了全样本依赖与全连接依赖之间的关系.首先,分别在全样本依赖集和全连接依赖集上建立等价关系,这两种等价关系都将作用相同的依赖视为等价依赖. 然后证明了在这两个等价关系下的商集分别构成么半群,并且这两个么半群是同构的.这就等于证明了全样本依赖类本质上等同于全连接依赖类.最后给出了一个关于全无环连接依赖的有趣结果.有关结果可以在关系数据库的设计中发挥积极作用.     

Discovering branching and fractional dependencies in databases

The discovery of dependencies between attributes in databases is an important problem in data mining, and can be applied to facilitate future decision-making. In the present paper some properties of the branching dependencies are examined. We define a minimal branching dependency and we propose an algorithm for finding all minimal branching dependencies between a given set of attributes and a given attribute in a relation of a database. Our examination of the branching dependencies is motivated by their application in a database storing realized sales of products. For example, finding out that arbitrary p products have totally attracted at most q new users can prove to be crucial in supporting the decision making.In addition, we also consider the fractional and the fractional branching dependencies. Some properties of these dependencies are examined. An algorithm for finding all fractional dependencies between a given set of attributes and a given attribute in a database relation is proposed. We examine the general case of an arbitrary relation, as well as a particular case where the problem of discovering the fractional dependencies is considerably simplified.