基于INTERNET的企业数据库同步设计方案

文章基于对企业数据库系统数据复制和数据同步的分析,对数据库的数据同步的概念、结构及设计方法进行了阐述,提出了一种全新的适合中国企业模式的数据库数据复制和数据同步的解决方案,并结合实际的实施案例对数据同步这一重要概念进行了初步的探讨。     

数据集成中消息中间件的设计

数据集成中的同步和复制是两个重要的方面，文章分析了分布式环境下的数据同步和复制方法，提出了异构数据库复制的消息中间件设计方案，它是上海交通大学数据中心建设的数据平台基础。     

基于多主体复制的Oracle数据同步研究

本文首先阐述了多主体复制的基本概念及其优点,然后分析了基于多主体复制的Oracle数据同步的基本原理,最后举例详细说明了实现基于多主体复制的Oracle数据同步的完整过程。     

VB中数据库同步复制冲突的检测与消除

基于Ｊｅｔ型数据库的ＤＡＯ编程接口提供了强大的数据库操作能力,其同步复制功能提供了开发中小型网络应用系统的基础。但是其开发文档中未提供检测与消除同步复制中的数据冲突的信息。本文基于ＶＢ讨论了ＤＡＯ中同步复制的若干问题,并提出了数据冲突的检测与消除的编程解决方法,进一步完善了基于Ｊｅｔ型数据库ＤＡＯ的功能。     

DAO中同步复制的应用及其数据冲突的检测与消除

在中小型ＭＩＳ系统中,与典型的客户机／服务器模式相比,ＤＡＯ的同步复制功能提供了一种灵活而高兴的解决方案,文章基于ＶＢ简介了ＤＡＯ的结构及其同步复制的实现机制,同时提出了一种解决同步复制中数据冲突的方法。     

动态IP环境下的SQL同步解决方案

对于大型企业来说,各分公司之间数据同步是一个很关键的应用。SQL Server本身的同步复制功能很强大,能很好满足数据同步的要求,但它的缺陷在于跨越互联网的同步复制只能是在双方都有固定IP的前提下进行。旨在解决一端有固定IP,另一端是动态IP的情况下使用SQL的同步复制功能来同步数据。     

DataSend:一种因特网环境下的数据库数据同步软件

在稳定性不好的网络环境下利用SQL SERVER数据库的复制功能进行数据同步容易造成数据的不完全一致。本文讨论了一个基于SQL SERVER复制方法和压缩技术的数据同步软件DataSend的设计和应用。DataSend通过建设中间层缓解了源数据库和目标数据库的压力;对传输数据进行压缩处理后再传输;通过状态来控制传输的准确性。从而提高了数据同步的传输效率、灵活性、安全性和准确性。     

乐观复制方法研究

在分布式数据库和数据仓库中,普遍采用数据复制的方法来提高数据的可用性和系统的性能。传统的同步复制方法由于高通信开销和操作延迟,会引起事务的大量阻塞和死锁,已很少采用。取而代之的是乐观复制方法,本文对数据冲突的处理采取乐现方式。本文对乐观复制的各种协议进行了分类和研究,并讨论了乐现复制的延迟与一致性问题。     

基于SQL server复制方法的数据库同步软件研究

在稳定性不好的网络环境下利用SQL server数据库的复制功能进行数据同步容易造成数据的不一致性。本文研究了一个基于SQL server复制方法和压缩技术的数据库同步软件DataSend的设计与应用。DataSend通过建设中间层缓解了源数据库和目标数据库的压力,对传输数据进行压缩处理后再传输;通过状态来控制传输的准确性,从而提高了数据同步的传输效率、灵活性、安全性和准确性。     

基于Socket的异地数据复制实现

实现异地分布数据库数据的一致性和同步性,一般都是通过数据库之间直接连接来实现数据的复制与更新,并且数据在网络中各节点的复制情况对用户是透明的.但在实际应用中,随着对数据安全性要求的提高,往往需要在网络、操作系统或者数据库之间采取一定的访问控制措施.针对以上情况,提出了一种基于Socket通信技术的异地数据复制方法,该方法通过定时扫描源数据库,筛选需要被同步的数据,然后利用Socket技术实现数据访问控制以及异地数据同步.     

数据库复制技术研究进展

在简要说明数据库复制技术目标的基础上,本文重点展开论述了数据库复制中的核心问题、解决方法与研究现状。通过对已有复制协议从不同侧面的分类,本文分析了各种协议不同的性能和可用性特点;通过对lazy和eager两种模式下复制协议的深入分析,揭示了技术发展的历史脉络和当前进展;对新兴应用需求进行归纳,得出了数据库复制技术可能的新发展方向。     

基于组通信技术的同步复制方法的研究

针对同步复制方法本身的缺点提出了一种新的研究思想，即引入组通信技术。利用组通信技术中关于转发信息的定序性质，借助天类队列的并发控制思想，很好地解决了复制领域中数据的一致性及通信量的问题。     

Comparing lazy and eager learning models for water level forecasting in river-reservoir basins of inundation regions

This study developed a methodology for formulating water level models to forecast river stages during typhoons, comparing various models by using lazy and eager learning approaches. Two lazy learning models were introduced: the locally weighted regression (LWR) and the k-nearest neighbor (kNN) models. Their efficacy was compared with that of three eager learning models, namely, the artificial neural network (ANN), support vector regression (SVR), and linear regression (REG). These models were employed to analyze the Tanshui River Basin in Taiwan. The data collected comprised 50 historical typhoon events and relevant hourly hydrological data from the river basin during 1996–2007. The forecasting horizon ranged from 1 h to 4 h. Various statistical measures were calculated, including the correlation coefficient, mean absolute error, and root mean square error. Moreover, significance, computation efficiency, and Akaike information criterion were evaluated. The results indicated that (a) among the eager learning models, ANN and SVR yielded more favorable results than REG (based on statistical analyses and significance tests). Although ANN, SVR, and REG were categorized as eager learning models, their predictive abilities varied according to various global learning optimizers. (b) Regarding the lazy learning models, LWR performed more favorably than kNN. Although LWR and kNN were categorized as lazy learning models, their predictive abilities were based on diverse local learning optimizers. (c) A comparison of eager and lazy learning models indicated that neither were effective or yielded favorable results, because the distinct approximators of models that can be categorized as either eager or lazy learning models caused the performance to be dependent on individual models.     

Eager Reclamation

Reclamation policies are presented which permit the reuse of storage for procedure instances before the procedures terminate. These eager reclamation policies are applicable under certain conditions and can reduce the total amount of memory needed for the execution of a program. The policies essentially differ in the amount of run-time checks needed and the reclamation opportunities. This eager reclamation strategy would be particularly useful when instances are implemented using register banks or in a microprocessor environment.     

Delay Optimization in Quorum Consensus

The management of replicated data in distributed database systems is a classic problem with great practical importance. Quorum consensus is one of the popular methods, combined with eager replication, for managing replicated data. In this paper we investigate the problems of delay-optimal quorum consensus. Firstly, we show that the problem of minimizing the total delay (or mean delay) restricted to a ring can be solved in a constant time in contrast to the existing approximation results. Secondly, we show that the problem of minimizing the total delay (or mean delay) is NP-hard. Thirdly, we present an approximate algorithm with an approximate ratio 2; and the approximate algorithm can guarantee the exact solutions for some specific network topology, such as trees and meshes. Finally, we present an improvement on the existing algorithm to solve the problem of minimizing the maximal delay; this reduces the time complexity from O(n ³ log n) to O(n ³) where n is the number of nodes.     

Delay Optimization in Quorum Consensus

The management of replicated data in distributed database systems is a classic problem with great practical importance. Quorum consensus is one of the popular methods, combined with eager replication, for managing replicated data. In this paper we investigate the problems of delay-optimal quorum consensus. Firstly, we show that the problem of minimizing the total delay (or mean delay) restricted to a ring can be solved in a constant time in contrast to the existing approximation results. Secondly, we show that the problem of minimizing the total delay (or mean delay) is NP-hard. Thirdly, we present an approximate algorithm with an approximate ratio 2; and the approximate algorithm can guarantee the exact solutions for some specific network topology, such as trees and meshes. Finally, we present an improvement on the existing algorithm to solve the problem of minimizing the maximal delay; this reduces the time complexity from O(n ³ log n) to O(n ³) where n is the number of nodes.     

Using Maude and Its Strategies for Defining a Framework for Analyzing Eden Semantics

Eden is a parallel extension of the functional language Haskell. On behalf of parallelism Eden overrides Haskell's pure lazy approach, combining a non-strict functional application with eager process creation and eager communication. We desire to investigate alternative semantics for Eden in order to analyze the consequences of some of the decisions adopted during the language design. In this paper we show how to implement in Maude the operational semantics of Eden in such a way that semantic rules can be modified easily. Moreover, other semantic features can be implemented by means of parameterized modules that allow to instantiate in different ways several parameters of the semantics but without modifying the semantic rules.     

多Agent系统中基于信任度评估模型的自动信任协商

在动态开放的系统中．由于Agent间交互存在着不确定性,安全成为一个重要问题。在现有的自动信任协商的基础上．考虑主观信任的作用．提出基于信任度评估模型的自动信任协商框架．详细介绍框架中的主要成分及其功能．着重讨论基于信任度评估模型的访问控制,以及在信任度评估模型基础上的两种协商对策：基于信任度评估模型的积极对策和基于信任度评估模型的谨慎对策。分别详细介绍采取上述两种对策的协商过程．并结合一应用实例说明基于信任度评估模型的积极对策的协商过程。