Prototype analysis and implementation of distributed network test system
Analysising and importing
The Prototype of The Distributed Network Exam System
Henan Siyi Automation Equipment Co., Ltd. Software Department
Henan Thinker Automatic Equipment Co. Ltd, GENG Baiqiang
Zi Xiren, Party School, Jiyuan Municipal Party Committee, Henan Province
Summary
With the continuous in-depth of the information construction of the locations and the comprehensive implementation of the mechanical safety management system, more and more local parts have put forward urgent needs. In order to meet the needs of the locations, we develop models in engineered software, using ModelMaker this Case tool, analyze, and design and develop a network based on COM and XML distributed multi-layer hybrid models. The test system, and provides an interface with the fingerprint management system, and it is reflected in the use of local locations. This article will introduce you to the prototype and implementation of the network test system.
Key words: COM ; UML; XML; Delphi; distributed; test system.
Abstract
With the going deep into development of locomotive information and putting locomotive security management system in practice in each field, more and more locomotive depots have a need to the network exam. To satisfy this requirement, we successfully developed a network exam system that it is a distributed multilayer mixed model based COM and XML technology, by using the tools of UML and ModelMaker that it is a tool of CASE provided by Borland company, and provided a interface to the finger printer system. in Executing in KUERLE locomotive depot, this system wins A Positive Reflection. In this Paper, I Will Introduce this Model and realized methods in network exam system in details to you.
Key Words: COM ; UML; XML;
Delphi
; Distributed; Exam System.
1 Introduction
With the increasing popularity of network technology and the importance of the Ministry of Railways on the information construction of the local area, the locations are now equipped with train operation safety monitoring equipment, and on this basis, the mechanical security management information system is built, and the information construction of the local area It has played a positive driving role. However, there is a phenomenon of software construction behind hardware construction. For example, the management segment management is still in traditional exam mode, not only low efficiency, but also there are many drawbacks, resulting in waste of information resources. Paper-free, networked network not only effectively reducing the workload of consulsters, better utilizing the advantages of computer and network, improving work efficiency, but also makes the exam more fair and fair. Based on this requirement, we have developed a set of performance stable, safe and reliable, easy to operate, which can meet the simultaneous network test systems that can meet the simultaneous use of large number of flight attendants. In addition, in order to strictly eliminate the cheating of the exam, the system also provides the function of fingerprint verification, which greatly improves the safety, fairness and impartiality of the exam. After use in the Urumqi Railway Bureau Korla locker, the effect is good, not only greatly promoted the information construction process of the Kurle's segment, but also makes the consumption personnel for the assessment of the flight attendant more scientifically, fair, fair, and efficient. Networked.
2 system development principle
2.1 System Target
The system should meet a large number of flight attendants anywhere, and can participate in the exam at any time, and automatically judge the score. The main functions provided by this system are as follows:
1. The flight attendant can examine the online exam. After the test, the computer is automatically judged by the computer, and records the scores, and the flight attendant can view the standard answer. If the test time is arriving, the system automatically prompts the volume and stops the answer.
2. The faculty can build, modify the question bank, modify the personal information of the flight attendant, monitor the situation of the examination room.
3. Administrators can establish documentation materials such as candidates, instructors, and arrange candid exams, and modify candidates and test spaces. Query candidates, monitoring examination room, and sets the number of exams and exams.
In addition, the test of the test is fair, fair, and the test paper test is randomly extracted from the question bank. To strictly eliminate the cheating behavior of the exam, the system should also provide fingerprint verification.
Further, considering the system's stability and execution efficiency, based on the network configuration of the Kurle locust, the system uses the architecture of the distributed three-layer C / S and B / S mixed architecture, namely: if the flight attendant is This paragraph is examined, you can select a touch screen test and workstation test mode of the C / S structure; if the flight attendant is experiencing an examination outside, you can select the workstation test mode of the B / S structure.
2.2 System mixing framework model based on C / S and B / S
The current software boundary comparative system structure model mainly: C / S structure model and B / S structure model. These two structures can be divided into two layers and multi-layer architectures, the main difference is whether middleware (e.g., COM or CORBA) is used to schema application server layer. Taking into account the specific needs of the license, the system uses the multilayer distributed network architecture model of C / S and B / S, as shown in Figure 1:
The structural model is designed to be designed with the advantages of distributed multi-layers C / S and B / S, and are divided into client layers, transaction logic layers, and data layers under normal conditions.
Client layer: Mainly used to meet various access requirements of the entire system and process the following work: Receive the user's input, analyze the user's input, and make a corresponding processing; send a data request to the server, display by the application server operation result. Customer layers are typically composed of client processes, and in this model, the client process mainly includes a process of dynamically created by IE browser and a process created by the client's exam workstation.
Transaction logic layer: Responsible for receiving requests from clients or vaults and processes the request to the underlying, while sending the request processing to the client or browser. The process of the transaction logic layer is mainly composed of middleware MTS / COM and some related processing processes. The Windows DNA (Distributed Internet Application Architecture, Distributed Network Application Structure) policy introduced under the Windows Platform. Take COM as an middleware in the Windows DNA policy. In the operating system of Windows 2000, COM has become part of the system. Com provides a series of strong support such as load balancing, object pooling, transaction characteristics, and procedures working in COM are protected by operating systems, thereby ensuring the security, stability and efficiency of the system. .
In this model, data dynamic operation is mainly achieved by ADO, ADO is Microsoft's current mainstream data access component, which provides an extremely simple object model, and encapsulated complex underlying access technologies.
Data layers: Mainly provide data services to transaction logic layers, such as storage data operation results, return data search results, etc.
This structural model overcomes the drawbacks of the second layer C / S, fully utilizing the advantages of distributed multi-layer C / S and multi-layer B / S, meet the needs of the local area in complex examination, excellent Using the business segment existing network resources, it is an effective integration, utilization, and expansion of existing network resources.
2.2.1 XML language
XML (Extended Markup Language) is a tag language, just like our familiar HTML, but XML tags are customized by people according to their needs, that is, any words and words can be used as labels. As long as the properties of the data can be accurately expressed. Accurate expression of data is the biggest benefit of XML. In addition, XML uses text to store its format, easy to communicate, communicate between the operating system, and adapt to the current development of the Internet.
XML has been widely used in just a few years, and the new software currently has almost supported XML. For example, Microsoft's .NET series software, Office series software, etc. It is not in a few years, XML will replace HTML to become a standard tag language on the Internet.
The advantage of introducing XML language expression data is to isolate data from the display and system processing of client data in the system, reduce the complexity of the development system, reduce system processing time, reduce network transfer, to improve system execution efficiency.
2.2.2 UML (Unified Modeling Language)
Unified Modeling Language, UML is a standardized modeling language for object-oriented software. Due to its simple, unity, it is possible to express the dynamic and static information in software design, which has become a de facto industrial standard for visual modeling languages.
From enterprise information systems to web-based distributed applications, even strict real-time embedded systems are suitable for modeling with UML. This is a hypothetical language that can describe the various views required to develop, and then assemble the system based on this.
The main advantage of this system introduces UML is to improve software development efficiency, reduce development time, and save development costs. Modeling in UML language should be best in Rational's ROSE tools. However, Rose is relatively expensive, and Rose is relatively large, it is not easy to use. The ModelMaker modeling tool produced by Borland has not only supports UML, but also has its own unique place on object modeling. Therefore, modeling tools will use ModelMaker.
2.3 Features of the system
(1), using distributed mixing frame modes (C / S and B / S), which can meet the needs of the maintenance section on the examination business in a variety of situations. (2), using multilayer frame mode, system performance, strong fault tolerance, and network load balancing function, with the ability to cope with large number of flight attendants to examine the ability of the examination business.
(3)
(4), using database secondary encryption technology, greatly improves the security of the database server, and constructs a network online test system with a high safety factor.
3 system development
3.1 General design plan
Distributed Network Online Examination System is a management information system based on distributed multi-layer hybrid architecture technology developed on a Windows platform, and its network structure is shown in Figure 2. Figure 3 is a page layout structure diagram in the web test mode. Its main process is that the user sets the corresponding operational operation based on the different user rights according to the authorization login. After the flight attendant is logged in, you can conduct an operation, see grades, and standard answers; after the instructor logs in, you can modify the personal information of the candidate (ie, the flight attendant), modify the question bank, modify the user password, and the monitoring exam; the administrator is logged in, except for the instructor Outside all functions, you can also review the question bank (only the question bank audited can be examined), set the test time, query, print test scores.
Exam workstation: Client procedures for flight attendants. It mainly provides a random problem based on system configuration, fingerprint verification login, test time prompt, automatic judgment grade, check the test score, and standard answers. The test workstation is divided into client programs and web methods in implementation. The former allows flight attendants to examine through the client program (support touch screen test mode), which allows flight attendants to conduct exams through railway private networks.
Test Settings Workstation: The client program for the test business. It mainly provides a modification of the question bank, reviewing the question bank, modifying candidates, setting candidates / test space, query / printing test scores, the import / export function of the question bank, and the monitoring exam.
Exam Application Server: Application Server of Network Online Test System. It mainly implements the package and multiplexing function of data buffering and test business logic. It is an examination workstation, an exam settings to set up a workstation and database server. The application server provides a rich interface that can increase or decrease the business rules through module mode. Considering the upgrade of the test business, the application server layer has reserved the interface of the new exam type, making it easier for future system expansion. In addition, in order to ensure the efficiency of the exam, the application server supports the database server mode of the dual-machine hot backup, that is, if the database server currently is in use, the backup database server in the system configuration automatically switches to the current database server, all of which It is carried out in the case where the user is not known to intervene. Through the efficiency of the application server layer, it is really easy to use the easy-to-the-job test business, powerful, stable performance, and strong modularity, and meets the high requirements of information construction in the new era.
The application server cluster shown in Figure 2 also includes a Windows IIS 5.0 web server except for the exam application server, which provides support and guarantees for the implementation of the test business on the railway private Internet. The database group refers to the SQL Server 2000 database and backup database in the background. The two database servers can automatically implement fault diagnostic switching modes through the intermediate-level application server.
Figure 3 shows the web implementation of the exam service. It provides an exam service to the flight attendant through the railway private network. Its business process is basically similar to the client program mode. The flight attendant logs in to the test web server through the IE 5.0 or higher browser. Test Web The server completes the operation according to different user privileges. The password verification components in the figure are called the login method for the three components of the instructor, the flight attendant, and the administrator, respectively. 3.2 System Security Solution
Network online test system requires data transmission through the network, so the security of the application server, the Web server and the database server must be planned from the system design. According to the actual situation of the Kurla port, we have adopted the following security measures:
(1), add reliable firewall, effective curbing of external malicious attacks;
(2) To convert the hard disk partition of the server (including the application server, database server, the web server) into NTFS format, and open respective permissions to users according to different needs;
(3), write key code as a DLL component, which not only enhances security, but also enhances the degree of modularization of the system to improve system performance;
(4), encrypt the critical data in the database, in the specific implementation, we use the AES (Advanced Encryption Standard) encryption technology;
(5) To apply the data backup and recovery function of SQL Server 2000 to ensure complete and security of database information.
4 system implementation
4.1 Selection of development platform
The distributed C / S and B / S mixed application architecture model used by Microsoft Company, and the development platform uses Windows 2000 Server, and the Database is selected for SQL Server 2000, and the web server program uses IIS 5.0. Due to the use of XML, the web client must be an IE 5.0 or higher browser to use this system. The client exam workstation can support Windows 98 / ME, 2000, XP, and 2003. Database Driver Select Microsoft MDAC2.7 components. .
4.2 Selection of Programming Tools
Currently, all popular development tools VC , VB and Delphi, etc., can achieve this procedure and the development of the middleware COM program. Use VC to get the best speed, maximum flexibility, the most powerful function, but the time and development cost to use the VC development system is enough to offset the benefits of him; using VB to develop spending time is Less, but VB's operational efficiency and VC differ. Delphi is a rapid development tool under Windows, which is Borland, has VB's development efficiency and running speed of VC programs, so it is used to develop this system is the most appropriate selection. In addition, in Delphi 7.0, the IntrawEB component is added, which can develop web applications directly in the Delphi7.0 environment. It is the best development tool for the hybrid architecture of this system.
4.3 Selection of XML and Web Editing Tools
Now there are many XML development tools, but many are not ideal, not using it is inconvenient, it is not good for Chinese. Finally, you can only write it by Notepad.exe under WINDOWS. Such efficiency is very low, perhaps because this reason XML does not have HTML applications.
The editing tool for the web page is better, and the most powerful use of Dreamweaver features is not two.
5 Conclusion
After the implementation of the Kurle locomotive, the system has a strong support of the segment leadership. After a period of operation, the user feels simple, stable, reliable, safe and efficient, and gives a high systematic evaluation. But we know, limited to factors such as energy, technology and time, there are many places that need to be improved: (1), random test volume generation algorithm is further strengthened. The current random algorithm is relatively simple. In actual use, the more complex and more efficient random algorithms can be used in combination with different situations.
(2) The test function needs to be increased. The current test type supports single item selection, multiple selection and judgment questions, etc., the type of test is to be further enriched, and the number of test questions in setting the examination subject can be added.
(3) System performance needs to be improved and improved. You can use the current SQL Server 2000 XML direct support to further improve program performance! In addition, the application server needs to enhance the function of load balancing.
references
[1] (US) GRADY BOOCH, JAMES RUMBAUGH, IVAR JACOBSON, "UML User Guide", Machinery Press, August 2001
[2] Li Wei, "Delphi5.x Distributed Multi-Technical Application - E-Commerce], Machinery Industry Press, May 2000
[3] Lin Jinqua, Jiang Hao, "Latest XML Getting Started", China Railway Publishing House, November 2001
[4] Pan Aimin, "COM Principles and Applications", Tsinghua University Press, November 1999
About the Author
[1] 百 强, Henan Siyi Automation Equipment Co., Ltd. Software Software Software Software, Main Research Direction: Multi - layer Distributed Systems, Components System.
[2] Yan Xiren, Henan Jiyuan Municipal Party School lecturer, main research: software engineering methodology, safety.
