Reliable distributed database management

A reliable distributed database must manage dispersed and replicated data, making them available to users in spite of hardware failures. In this paper we study the algorithms and techniques that can achieve this reliability. Three scenarios are considered for reliable (i.e., nonpartitionable) networks. In the first, data are distributed but not replicated; in the second, data are replicated; and in the third, both data and processing are fully replicated in an n-modular redundancy strategy. A brief survey of methods for handling network partitions is included.     

An Ada-compatible distributed database management system

Adaplex is an integrated language for programming database applications. It results from the embedding of the database sublanguage Daplex in the general-purpose programming language Ada [1]. This paper describes the design of DDM, a general-purpose distributed database management system implemented in Ada that supports the use of Adaplex as interface language. There are two novel aspects in the design of this system. First, this is the first full-scale distributed database system to support a semantically rich, functional data model. DDM goes beyond systems like Distributed INGRES and R^*(which are based on the relational technology) in providing advanced data modeling capabilities and ease of use. Second, this is the first full-function distributed DBMS designed to be compatible with the Ada programming environment. The coupling between Ada and Daplex has been achieved at the expression level which is much tighter than the statement level integration attained in previous systems. This tight coupling poses new implementation problems but also creates new opportunities for optimization. The current paper highlights the Adaplex language and discusses innovative aspects in DDM's design that are intended to meet the dual objectives of good performance and high data availability.     

A retrospective of R*: A distributed database management system

This paper discusses the experience gained during the implementation of a prototype distributed database management system. The R^*prototype supports transparent distribution of a relational database which is accessed using the SQL language for data definition and manipulation. While supporting autonomy among the participating sites, R^*also emphasizes good performance for both local and multi-site operations. During the implementation of the R^*prototype, we were guided by a few key objectives and encountered several interesting problems. This paper will discuss the guiding objectives of the R^*effort, as well as several areas of the implementation which presented special difficulties or were simplified by design decisions.     

基于高校教材管理系统的分布式查询优化技术

分析了分布式数据库查询优化要考虑的问题,然后描述了分布式数据库查询优化的过程,最后给出了高校教材管理系统中可以选择的分布式查询策略。     

分布式数据库安全机制探究

文中分析的是分布式数据库的安全机制,基于其结构和存在的安全问题,提出了分布式数据库的安全措施,并分析了其在SQL Server中的实现。     

基于DAI中间件的异构数据库集成

在研究异构数据库中数据集成的基本原理基础上,提出了数据库集成模型实现策略,即在异构数据库之间构建了一个中间层软件--"虚拟数据库系统",经授权认证的合法用户通过"虚拟数据库系统"提供的标准访问接口及统一数据格式对环境中各种分布的、异构的、不同种类的数据资源进行动态访问和集成.     

基于WDM网络分布式物理层损伤感知数据库

网络向高速率和高容量不断升级,在选路过程中自适应地规避物理层损伤进而实现高质量的传输服务已成为亟待解决的问题,而物理层损伤信息的感知和保留是其中的关键。文章通过分析物理层损伤参数,建立分布式PLID(物理层损伤感知数据库)的信息表征表,借鉴流量工程数据库标准协议,扩展其中的OSPF-TE(基于流量工程开放式最短路径优先算法)协议,定义一个新的Opaque LSA(链路状态通告)类型即PLI-LSA(物理层损伤信息的LSA),实现了PLID的建立和更新。比较数据库不同更新方式的控制开销,发现采用基于阈值的更新方式较合适,可满足不同的服务质量对不同波长信道传输质量的要求。     

Deadlock resolution for distributed real-time database systems

There are few studies of deadlock resolution in the real-time distributed database environment. A specially designed distributed deadlock detection algorithm known as the Enhanced Probe-Based Algorithm (EPBA) was evaluated by the authors and has found to be very effective. The present work is carried out to evaluate the EPBA for the firm real-time distributed database environment. The study also compares its performance with other existing deadlock resolution algorithms such as the timeouts algorithm and the global sequential locking algorithm. Results indicated that under high data contention and with slack transaction deadlines, the EPBA approach outperforms all the other deadlock resolution methods.     

全分布式位置管理策略的负载和位置更新性能研究

分布式位置管理策略及其分布式数据库结构与传统位置管理策略和HLR－VLR结构有显著区别，本文基于一种对DDB结构新的性能估计方法，从用户的移动性概率分布出发，对DDB结构下的数据库负载和位置更新性能进行了研究。     

BilVideo: a video database management system

The BilVideo video database management system provides integrated support for spatiotemporal and semantic queries for video. A knowledge base, consisting of a fact base and a comprehensive rule set implemented in Prolog, handles spatio-temporal queries. These queries contain any combination of conditions related to direction, topology, 3D relationships, object appearance, trajectory projection, and similarity-based object trajectories. The rules in the knowledge base significantly reduce the number of facts representing the spatio-temporal relations that the system needs to store. A feature database stored in an object-relational database management system handles semantic queries. To respond to user queries containing both spatio-temporal and semantic conditions, a query processor interacts with the knowledge base and object-relational database and integrates the results returned from these two system components. Because of space limitations, we only discuss the Web-based visual query interface and its fact-extractor and video-annotator tools. These tools populate the system's fact base and feature database to support both query types.     

分布式多空间数据库系统的集成技术

分布式多空间数据库系统是实现异构空间数据源的互操性和实现空间信息共享的有效途径,而且也是理论上的热点课题。本文通过对其基本概念的界定以及对空间数据分布特征的探讨,试图提出多空间数据库系统集成的基本思路,为航空维修工作提供支持。     

Evaluation of transitive closure in distributed database systems

A special schema is constructed to represent the data of a binary relation so that the transitive closure can be evaluated efficiently in distributed database systems. The method is economical in communication cost and at the same time preserves the fast access paths for efficient parallel processing of transitive closure at local sites. Updating of data is also discussed     

Some experiences with a distributed database testbed system

DDTS (Distributed Database Testbed System) was developed for the purpose of evaluating alternative approaches and algorithms for managing data stored in several databases on different machines. An overview of the system and information architectures of DDTS, as well as an example of the execution of a distributed request, are presented. The results of experiments with three query optimization algorithms are summerized. Our approach for dealing with semantic integrity constraints in a distributed system is reviewed. By sacrificing the enforcement of semantic integrity constraints that span sites, DDTS can be used as a federated distributed database management system.     

分布式数据库在数字林业系统中的应用研究

将计算机技术、网络技术和数据库技术应用到林业系统的建设中,实现林业数字化,是国家林业部的一项重大举措。现主要讨论了数字林业建设的重要性,以及在数字林业体系中进行分布式的林业基础信息数据库的构建方法。     

分布式数据库安全代理的研究与实现

针对传统的分布式数据库系统内访问控制方案存在滞后的弊端,数据传递通道存在潜在安全隐患的问题,研究并实现了分布式数据库安全代理系统。该系统分别封装了代理客户端以及代理服务端,为其他模块进行调用提供基础,通过组件技术实现代理客户端以及代理服务端的设计,给出设计模型内各模块的运行原理和功能。通过代理客户端中的组件创建同应用程序的接口以及同网络通信客户端的接口实现访问数据库的功能,向代理服务端反馈处理后的访问结果。给出网络通信平台设计过程以及代理客户端、服务端设计过程。经测试表明,分布式数据库安全代理系统可实现用户和服务器间的安全通信,可有效实现身份认证,访问性能高,可靠性高。     

基于虚拟数据库技术的异地异构数据源整合

传统异地异构数据的整合方法存在查准性能差的问题,文中为此提出基于虚拟数据库技术的异地异构数据源整合方法。构建虚拟数据库异地异构数据的传输负载模型及数据存储结构,提取数据存储结构的稀疏性特征,并挖掘虚拟数据库异地异构数据的属性关联规则特征量,利用特征量融合异地异构数据的模糊信息,建立数据整合模型,实现虚拟数据库异地异构数据源整合。仿真结果表明,采用该方法进行虚拟数据库异地异构数据源整合时间的开销小,数据库的查准率较高。     

基于分布式处理技术的物联网数据库研究和设计

针对物联网中的数据库管理问题,通过对物联网技术的研究,结合分布式处理技术、P2P(对等网)点云计算技术,提出了一个基于分布式处理技术的物联网数据库设计方法。在此以医疗系统物联网为例,验证了该方法在一定程度上能够解决物联网中的数据库管理问题,从而为物联网技术与数据库技术、网络技术、中间件技术等的技术结合提供了技术支撑。     

分布式计算机数据库系统设计与研究

文章主要分析了分布式数据库设计的特点、方法与技术，综述了自顶向下和自底向上分布设计方法的理论和技术，主要论述了DATAID-D 自顶向下设计方法，并分析了分布式计算机数据库系统功能的实现。     

分布式计算机数据库系统设计与探究

文章主要分析了分布式数据库设计的特点、方法与技术,综述了自顶向下和自底向上分布设计方法的理论和技术,主要论述了DATAID-D 自顶向下设计方法,并分析了分布式计算机数据库系统功能的实现。     

企业管理中计算机数据库系统的应用

计算机数据库(Database)是存储在计算机内,为达到一定的目的而组织起来的有结构的数据的集合。企业在对网上客户数据的采集,归纳整理,以及企业内部网络构建和企业自身数据库管理系统,包括资源规划,客户资源管理等都属于库数据库应用方案。数据库是计算机的一个重要领域,数据库技术的诞生以来在生产、生活、工作、学习等方面给人们带来了巨大的便利。计算机数据库系统应用于企业信息管理有利于提高信息管理的科学性和现代性,有利于提高信息管理的效率。