数据库存取

The application of this technique in data access object is implementd through repacking the interface between application program and database system.

现代数据管理几乎都是以数据库作为其核心的，同时，现实世界中越来越多的应用要求对数据的"定时"存取和对"短暂有效"数据的存取，实际操作越来越趋于复杂，软件的设计也越来越复杂，数据库访问和处理的速度已经越来越重要了，实时数据库在这种情况下提了出来。

For a database application, the database access method is one of those.

对于一个数据库应用来说，数据库存取方法就是其中之一。

It will promote the work efficiency and quality, and also gives an example of network applications to other specialty of water conservancy and hydroelectricity industry.

基于Web的监测设计图文档管理系统的研究与实现，填补了这一领域信息化建设的空白，为设计人员提供了一个方便、高效的网络化资料管理与资源共享的平台，必将极大地促进工作效率和质量的提高，有较好的实用价值，同时，对DWG格式文件的网络传输及数据库存取的处理方式的研究与实现，也为水利水电行业其他类似专业的应用提供了一个思路和方法，有一定的借鉴意义。

Visual Basic has strong data stock that fetches ability It can not merely support Ms Access data base directly , Enable it to support FoxPro、dBASE outside data bases through ISAM driver that inside installed its indirectly.

Visual Basic有着强大的数据库存取能力，不仅能够直接支持Ms Access数据库，而且通过其内部安装的ISAM驱动程序使它能间接支持FoxPro、dBASE等外来数据库。

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。

The paper mainly concerns about:(1)Proposing the idea of completing the job using GIS software by discussing deficiency of the traditional transportation job;(2)Discussing the transportation plan algorithm and the flow, in this foundation, designing the transportation model programming realization flow chart;(3)With the comparison of the domestic and foreign GIS software platform, determining ArcGIS Desktop which has large drawing edit and spatial analyse functions as the development platform of transportation planning;(4)In the data organization and the database establishment, by using the recent object-oriented spatial data— Geodatabase and UML, completing the system database design and establishment, including spatial database, attribute database as well as transportation network database

详细研究内容如下：(1)论述了传统交通规划软件存在问题，提出了利用GIS平台开发交通规划系统的基本思想；(2)论述了交通规划的算法和流程，在此基础上，设计了交通模型编程实现的流程图；(3)通过比较国内外GIS软件平台，选定了具有强大图形编辑和空间分析功能的ArcGIS桌面版为交通规划系统的开发平台；(4)在数据的组织和数据库的建立上使用新的面向对象的空间数据—Geodatabase，并利用统一建模语言UML完成了系统数据库的设计与建立，包括空间数据库，属性数据库以及交通网络数据库；(5)论述了系统编程实现的基本方法，在ArcMap下采用VBA编程方法自由地定制了系统界面；(6)利用ADO Data和数据网格控件存取交通规划系统预测功能所需的数据库；(7)采用VB对ArcObject控件扩展开发方式，实现系统功能的开发，即利用COM技术的扩展性在VB中创建ActiveX动态链接库来实现特定的系统功能，并集成在ArcMap中运行；(8)系统完成了交通发生预测、交通分布、缓冲区分析、道路的网络分析、公交

In database system, normally the database management system will in charge of retrieving and storing of data.

在数据库中，一般存取时的细节是由数据库管理系统管理，应用程序不必了解数据库的软件和硬件的改变。

The application of this technique in data access object is implementd through repacking the interface between application program and database system.

现代数据管理几乎都是以数据库作为其核心的，同时，现实世界中越来越多的应用要求对数据的&定时&存取和对&短暂有效&数据的存取，实际操作越来越趋于复杂，软件的设计也越来越复杂，数据库访问和处理的速度已经越来越重要了，实时数据库在这种情况下提了出来。

When we operate all accessing databases in encapsulation at Data Access Layer by ActiveX DLL packages (DAL layer, Namely data access layer),and operate all business logic or transaction processings in encapsulations at Business Logic Layer ( BLL layer, namely business logic layer), ASP dynamic webpages are offered to the interface of user for Presentation Layer ( PL layer, Namely present layer).

使用ActiveX DLL组件将对数据库的存取操作全部封装在Data Access Layer层（简称DAL层，即数据存取层），将商业逻辑或事务处理全部封装在Business Logic Layer层（简称BLL层，即商业逻辑层），提供给使用者的界面就是Presentation Layer层的ASP动态网页。

If a "reasonable" notion of database consistency is to be supported (I.c. the database system is to enforce it automatically), there are bound to be" conflict" situations where one transaction comes into an access conflict against some other transaction. If await is to be avoided,some means of a negotiated settlement of the conflict must be provided, thereby dragging the users into the details of concurrency control.The single-database model is more appropriate-ate than the multiple-database model in an environment where it is difficult to determine in advance logical partitions of the database that correspond to work to be performed, and the users closely cooperate.

如果一个数据库一致的合理观念要得到支持（即数据库系统要自动实行这个观念）、一定会有矛盾的情形产生、在这种情形中一个业务与其它业务产生存取矛盾如果要避免等待，就必须提供某种协商解决矛盾的方法，从而迫使用户详细了解并行控制单一数据库模式在某一种环境中比多个数据库模式更恰当，在这个环境中，要事先确定与要执行的工作相适应的数据库的逻辑分割是很难的，同时用户们又紧密地合作在一起。

This one mode pays close attention to network credence foundation of the businessman very much.

这一模式非常关注商人的网络信用基础。

Cell morphology of bacterial ghost of Pasteurella multocida was observed by scanning electron microscopy and inactivation ratio was estimated by CFU analysi.

扫描电镜观察多杀性巴氏杆菌细菌幽灵和菌落形成单位评价遗传灭活率。