CLIENT/SERVER环境下数据库系统完整性约束及其措施

本文主要讨论ＣＬＩＥＮＴ／ＳＥＲＶＥＲ环境下数据库系统完整性约束的性质、特征及其在数据库系统中的重要性，并阐述了在ＣＬＩＥＮＴ／ＳＥＲＶＥＲ环境中如何保障数据库系统完整性的一些措施。     

演绎数据库中规则维护器的设计与实现

完整性维护是演绎数据库管理中的重要组成部分。首先给出演绎数据库系统的总体结构，然后重点介绍规则维护器的设计和实现，并阐述了规则操纵中完整性维护的基本算法。     

多数据库系统中的模式映射方法

多数据库系统一般具有四级模式结构，全局用户只能访问全局模式，而最终的数据必须从各局部数据库系统中获得，因此必须建立多数据库系统的模式映射，它表示了局部模式通过输出模式集成为全局模式的相应转换。本文给出了一种多数据库系统中的模式映射方法，并使用 模式映射树来存储和表达这种模式映射。     

基于分布对象Web的主流数据库集成系统

面向新一代的分布式对象Web体系结构，将全局数据库技术，全局数据库事务管理技术，主流数据库对象化组件技术和先进的CORBA对象技术综合成一体，在支持异构分布式系统的CORBA机制，全局数据库模式，全局查询语言的定义，语法和语义分析，查询优化，主流数据库的对象化表示，事务的管理，并发控制，安全管理，全局事务的完整性处理，主流数据库的集成工具，多数据库系统的管理和维护策略等方面，针对实用化的目标开展研究并加以实现。     

Oracle主动数据库机制的应用

通过Oracle提供的约束定义和触发器定义,把应用数据库设计成主动数据库系统,可以在数据库端由服务器监控数据库的状态和操作,可以自动控制数据的完整性和安全性,还可以自动生成跟踪、日志、审计等用户感兴趣的信息.     

基于多方面完整性检测的移动数据库同步机制

在三级复制移动数据库系统的基础上,提出了参照完整性约束检测算法、移动数据库特有完整性约束检测和消解算法,推广了建表时的check以及断言冲突检测及消解的算法,最终设计出一种多方面完整性检测的移动数据库同步机制.     

基于9210工程Sybase数据库信息系统的保护策略

基于9210工程的Sybase数据库，本文就其安全性、完整性、并发控制、故障恢复这四个方面分析并论述数据库系统的保护机制及其实现方法，以在应用中更好地维护数据库系统。     

P2P多数据库系统中的事务并发控制研究

P2P多数据库系统是一种分布式的数据库系统,它是P2P计算系统和传统数据库系统的结合体.P2P计算系统的动态性使得P2P多数据库系统的事务管理缺少全局控制机制.在事务传播过程不存在循环的前提下,文章提出了一种保证P2P多数据库系统中事务全局串行化的并发控制协议,它通过控制一系列全局事务传播过程中每个熟识关系的两级串行化来实现.     

引用完整性与隐通道

该文提出了一类数据库系统所特有的隐通道一利用引用完整性约束传送信息的隐通道,分析了它们的带宽,并提出了处理这类隐通道的方法。     

基于双重库结构的数据库系统容错设计技术

本文在传统差分文件技术的基础上提出了一种采用双重库结构的数据库系统容错设计新技术,并将其实际应用于多个信息系统的设计中。这些系统除了完成正常的事务管理(包括数据维护)功能外,还具有独特的适用于微型机环境的可靠性控制及完整性控制功能。理论和实践表明,基于双重库结构的数据库系统具有良好的可靠性和完整性性能。该项数据库容错技术可推广至微型机DBMS及数据库应用系统的设计中。     

Concurrency control in hierarchical multidatabase systems

Over the past decade, significant research has been done towards developing transaction management algorithms for multidatabase systems. Most of this work assumes a monolithic architecture of the multidatabase system with a single software module that follows a single transaction management algorithm to ensure the consistency of data stored in the local databases. This monolithic architecture is not appropriate in a multidatabase environment where the system spans multiple different organizations that are distributed over various geographically distant locations. In this paper, we propose an alternative multidatabase transaction management architecture, where the system is hierarchical in nature. Hierarchical architecture has consequences on the design of transaction management algorithms. An implication of the architecture is that the transaction management algorithms followed by a multidatabase system must be composable– that is, it must be possible to incorporate individual multidatabase systems as elements in a larger multidatabase system. We present a hierarchical architecture for a multidatabase environment and develop techniques for concurrency control in such systems. Edited by R. Sacks-Davis. Received June 27, 1994 / Accepted September 26, 1995     

Using tickets to enforce the serializability of multidatabasetransactions

To enforce global serializability in a multidatabase environment the multidatabase transaction manager must take into account the indirect (transitive) conflicts between multidatabase transactions caused by local transactions. Such conflicts are difficult to resolve because the behavior or even the existence of local transactions is not known to the multidatabase system. To overcome these difficulties, we propose to incorporate additional data manipulation operations in the subtransactions of each multidatabase transaction. We show that if these operations create direct conflicts between subtransactions at each participating local database system, indirect conflicts can be resolved even if the multidatabase system is not aware of their existence. Based on this approach, we introduce optimistic and conservative multidatabase transaction management methods that require the local database systems to ensure only local serializability. The proposed methods do not violate the autonomy of the local database systems and guarantee global serializability by preventing multidatabase transactions from being serialized in different ways at the participating database systems. Refinements of these methods are also proposed for multidatabase environments where the participating database systems allow schedules that are cascadeless or transactions have analogous execution and serialization orders. In particular, we show that forced local conflicts can be eliminated in rigorous local systems, local cascadelessness simplifies the design of a global scheduler, and that local strictness offers no significant advantages over cascadelessness     

On rigorous transaction scheduling

The class of transaction scheduling mechanisms in which the transaction serialization order can be determined by controlling their commitment order, is defined. This class of transaction management mechanisms is important, because it simplifies transaction management in a multidatabase system environment. The notion of analogous execution and serialization orders of transactions is defined and the concept of strongly recoverable and rigorous execution schedules is introduced. It is then proven that rigorous schedulers always produce analogous execution and serialization orders. It is shown that the systems using the rigorous scheduling can be naturally incorporated in hierarchical transaction management mechanisms. It is proven that several previously proposed multidatabase transaction management mechanisms guarantee global serializability only if all participating databases systems produce rigorous schedules     

基于CSCW下Web多数据库协同管理的研究

Web已经为用户合作提供了良好的环境。基于协作的企业多数据库的特点，分析了CSCW环境下数据库多态性、自制性和分布性，提出了CSCW环境下基于Web的多数据库协同管理的模型以及用户程序对多数据库访问的连接语言模型和实现策略。     

基于CORBA/XML的多数据库系统研究与实现

多数据库系统是实现多个分布的异构数据源数据共享和互操作的有效途径．首先介绍了一种基于ＣＯＲＢＡ的多数据库系统体系结构模型，然后提出了一种面向ＸＭＬ的公共数据模型ＸＩＤＭ，这些模型能很好适应多数据库系统分布性、自治性和异构性等特点．还对基于这些模型所实现的一个多数据库原型系统Ｐａｎｏｒａｍａ进行了介绍．     

一种多数据库事务模型

分析了多数据库系统中事务的特征，给出了多数据事务和事务经历的形式化描述，在此基础上，提出了多数据库事务正确性标准MDB-可串行化，最后给出了,基于MSG图的多数据库串行化定理。     

一种多自治域层次互操作模型的系统框架

数据互操作是信息集成领域需要解决的关键问题。联邦数据库和多数据库是解决分布式异构环境中多个数据源的集成与互操作的两种方法,但它们各有优缺点。完全的集中不能保证局部系统的自治,全部的分散又不能保证系统之间的共享和互操作。在分析联邦数据库与多数据库特点与差异的基础上,提出了一种多自治域的层次互操作模型MDHI,通过对Panorama多数据库系统进行扩展,给出了一种基于WebService的PanoramaWebOne系统框架。这种框架既满足了局域范围内的集成和处理效率,又提供了一种集成广域范围内多种异构数据源的方法,更加符合当前实际应用的需要。     

多数据库系统中查询分解算法的研究

多数据库系统允许用户使用一个集成模式和简单的全局查询语言同时访问多个异构的、自治的数据库系统。全局查询分解处理是多数据库系统中的一个很重要的问题。本文给出了一种多数据库环境中的模式信息管理方法,基于这些模式信息,我们提出一种易于实现的查询分解算法。由于多数据库查询分解处理与模式集成的实现紧密相关,所以本文对多数据库系统的模式集成作了一些描述。     

Query optimization in multidatabase systems considering schemaconflicts

In a multidatabase system, the participating databases are autonomous. The schemas of these databases may be different in various ways, while the same information is represented. A global query issued against the global database needs to be translated to a proper form before it can be executed in a local database. Since data requested by a query (or a part of a query) is sometimes available in multiple sites, the site (database) that processes the query with the least cost is the desired query processing site. The authors study the effect of differences in schemas on the cost of query processing in a multidatabase environment. They first classify schema conflicts to different types. For each type of conflict, they show how much more or less complex a translated query can become in comparison with the originally user-issued global query. Based on this observation, they propose an analytical method that considers the conflicts between local databases and finds the database(s) that renders the least execution cost in processing a global query. This research introduces a new level of query optimization (termed the schema-level optimization) in multidatabase environments. The results provide a new dimension of enhancement for the capability of a query optimizer in multidatabase systems     

Quantification of autonomy on multidatabase systems

Amultidatabase system is an interconnected collection of autonomous databases each managed by an autonomous database management system (DBMS). When integrating multiple DBMSs, the key is the autonomy of the underlying participants. Much research has been undertaken in the past five years aimed at describing and building an integrated multidatabase system, but to date the termautonomy has only been defined intuitively. This article provides a rigorous definition for autonomy tailored to the multidatabase environment specifically but applicable to any system environment that involves the collaboration of autonomous participants. The major contribution of this article is a technique that measures autonomy along multiple dimensions so a single numeric value describing the amount of autonomy violated by a particular system design is quantified. This has a two-fold implication. First, the technique described forces researchers to consider autonomy from several different aspects that may not be the central focus of their research, but must be considered because assumptions made regarding one aspect of a system may have implications in other areas. Second, the value can be used as a measure for direct comparison among different systems or proposals. Finally, the article demonstrates the quantification technique's applicability by applying it to several recent multidatabase research efforts.