分布式数据库

Namely, using the centralized and distributed database design optimizes the configuration of simulation database of Air fleet fighting DIS system and ~duces network flux.

即利用集中和分布式的数据库结构对机群作战分布交互式仿真系统的数据库进行了优化设计，减少了网络数据流量。

The algorithm of the division of the GML spatial date, and the distributed spatial data base and the metadata base were designed.

同时设计相应的分布式空间数据库和空间元数据库。

People begin to focus on the development of distributed database when traditional database technology and Internet becoming more and more perfect.

随着传统的数据库技术日趋成熟，计算机网络技术的飞速发展和应用范围的扩大，以分布式为主要特征的数据库系统的研究受到人们的关注。

In accQrdance with the concerned isomerism and distributivity of the database system in the long-distance education, and variety of database inter-connectivity technology, we law lessons from the successful application in TCP/IP communication protocol, and adapt to use the Layer thought to realize the share of distributive isomeric database information.

针对目前远程教育中所涉及的数据库系统的分布性和异构性，数据库互连技术的多样性，本文欲借鉴网络通信协议的成功之处，采用分层结构的思想去实现分布式异构数据库信息的共享。

The distributed Web technology is a combination of network and database technologies and it is also an application of multilayer distributed application.

分布式Web技术是网络技术和数据库技术的一种结合，也是一种多层分布式应用。

It becomes more difficult to manage, integrate and share the control system real-time data when we set up the industrial real-time database because of complicated affair between every department and isomeric character of the system. A three-level-structure model and the method to establish database is provided based on CORBA criterion with its character of being regardless of programming languages, hardware platform and network protocol . A universal real-time database faces multi-system is also set up by learning the distributed criterion, it can realize the request broker , and the application software can visit the database pellucidly ; Thus the power station simulation model can be linked with the control system such as infi90 , ovation and be made use of the control object , a closed simulation and control experiment system is set up. Further more we can build an integrate automatic experiment platform from the simulation object of power plant to the process control and the to SIS. Li Ming(Control Theory and Control Engineering)Directed by associate prof. Lin Yongjun

在创建工控领域实时数据库时，企业各部门间的复杂事务及内部异构性给实时数据的管理、集成和共享带来了一定的困难，根据CORBA规范具有语言无关性、平台无关性和网络协议无关性的特点提出基于分布式计算规范CORBA的三层体系结构模型及建立与维护实时数据库的方法和途径；通过CORBA规范建立面向多个分散控制系统的通用实时数据库，实现数据访问代理，使应用软件可以透明地对实时数据库进行访问、存取、管理；将Infi90、Ovation分散控制系统与火电厂仿真机模型进行有效的互连，以全物理过程仿真数学模型为对象，构建了闭环控制仿真实验研究系统，实现数据的高效连通及管理；进而通过基于CORBA的实时数据库构建一个从火电厂仿真机对象到过程控制设备再到SIS系统的综合自动化试验平台。

This thesis deeply researches the J2EE security strategy on the application tier of enterprise system. The security strategy predigests the information security model and meets the security requirements expediently. But there are some disadvantages when the security requirements become more complex. The expositive security on the Web-Tier can not offer more information for authentication; there is no authentication for EJB-Tier to use, make the EJB-Tier depend on the Web-Tier; J2EE uses database or application server to manage the role information. Use database to manage the role information will increase the complex of enterprise application, and the way of application server will reduce the ability of migrate other J2EE platform. To solve these problems, the thesis designs an improved security strategy model.

本文从企业级系统应用层安全的角度出发，深入研究J2EE多层体系结构的安全策略模型。J2EE提供的安全策略简化了系统的信息安全模型，能够很方便地满足基于J2EE的分布式应用系统的安全需求，但是在面对更加复杂的安全需求时，J2EE安全策略在验证授权和角色管理中还存在不足之处：其在Web层的声明式验证机制无法为用户提供更多验证信息，可扩展性较差；在EJB层缺少业务逻辑层可供采用的验证机制，而是借助于Web层的验证机制，其耦合程度较高有悖于业务逻辑分离于表现逻辑的原则；在角色管理方面，J2EE采用数据库或者应用服务器来管理角色信息，其中，数据库管理角色的方式增加了应用开发的复杂度，应用服务器管理角色降低了系统的可移植性，两者都具有片面性。

To solve this problem of keeping date consistence in the heterochronous environment, the paper puts forward a synchronous updating system model, which applied Web Service to capture, store and then transfer updated things in the homogeneous distributed database system and farther implement the system's model of data synchronization, In the design of this model, the concurrency control of distributed things and the method of failure inspection are discussed and solved successfully.

针对异构或异质环境下保持数据一致性的问题，给出一个在分布式异质数据库中，通过Web Service技术，对数据库更新事务进行捕捉、存储后转发，进而实现数据同步更新的系统模型。

Once detected, nondistributed and distributed deadlocks are handled by the database and application in the same way.

无论分布式或非分布式死锁，在数据库及应用程序中的处理方法都是相同的。

In order to establish the systematic structure of Web Serves and enhance reusability of the software and safety of application syste m,this paper lays emphasis on researching and analyzing technology of loginning,data enciphering,database connection visiting,ensuring database safety,defending Web attack and reserving data to avoid any disaster and then gives some better corresponding solutions.

为了搭建多层结构的分布式Web应用系统的Web Servers体系结构，提高软件的可重用性及应用系统的安全性，本文重点对遥程数据库维护中的登录技术、数据加密技术、数据库连接访问技术、数据库安全技术、防Web攻击技术及远程数据容

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。