Abstract: In the case of full analysis and comparison of B / S structure and C / S structure, the future development prospects are briefly described, and a new architecture is proposed. Combining B / S and C / S, the component technologies COM + and AcdveX are applied to the server and client respectively, so as to develop an efficient and safe application system.
In recent years, with the continuous development of network technology, especially the rapid development of Web-based information publishing and retrieval technology, Java computing technology and network distributed object technology, many application systems have become more flexible from C / S structure. The evolution of the B / S multi-level distribution structure has made the network architecture of the software system enter a new stage. Recognizing the characteristics of these structures and selecting the system according to the actual situation is critical to the successful development of an MIS system.
1 C / S structure and B / S structure
1.1 C / S structure
C / S structure, namely Client / Server (client / server) structure. This structure puts the database content on a remote server, and installs the corresponding software on the client. C / S software generally uses a two-layer structure, and its distribution structure is shown in Figure 1. It consists of two parts: the front end is the client, that is, the user interface (Client) combines presentation and business logic, accepts the user's request, and makes a request to the database service, usually a PC; the back end is the server, which is data management (Server) submits the data to the client, and the client calculates the data and presents the results to the user. It also provides complete security protection and data integrity processing operations, and allows multiple customers to access the same database at the same time. In this structure, the hardware of the server must have sufficient processing power, so as to meet the requirements of various customers.
The C / S structure is very mature in technology. Its main features are strong interactivity, safe access mode, low network communication volume, fast response speed, and conducive to processing large amounts of data. However, the program of this structure is targeted development, the change is not flexible enough, and it is more difficult to maintain and manage. Usually limited to small local area networks, it is not conducive to expansion. In addition, because each client of this structure needs to install the corresponding client program, the distribution function is weak and the compatibility is poor, and rapid deployment installation and configuration cannot be achieved. Therefore, it lacks versatility and has relatively large limitations. Technical personnel with a certain professional level are required to complete.
1.2 B / S structure
B / S structure, namely Browser / Server (browser / server) structure, is to install and maintain only one server (Server), and the client uses browser (Browse) to run the software. It is a change and improvement of the C / S structure with the rise of Internet technology. Mainly using the continuously mature WWW browser technology, combined with a variety of Script languages ​​(VBScript, javascript ...) and AcTIveX technology, it is a brand-new software system construction technology. 
The B / S three-tier architecture adopts a three-tier client / server structure, adding a layer of structure at the data management layer (Server) and user interface layer (Client), called middleware, which makes the entire system structure Become three layers. The three-tier structure is emerging with the maturity of middleware technology. The core concept is to use middleware to divide the application into three different processing levels: presentation layer, business logic layer, and data storage layer, as shown in Figure 2. The division of the three levels is logically divided, and the specific physical division method can have multiple combinations. As the basic platform for constructing a three-tier structure application system, middleware provides the following main functions: responsible for the connection and communication between the client and the server, and the server and the server; achieving efficient connection between the application and the database; providing the development of a three-tier structure application , Operation, deployment and management platform. This three-layer structure is independent from layer to layer, and changes in any layer will not affect the functions of other layers.
In the B / S architecture system, the user sends requests to many servers distributed on the network through the browser, and the server processes the requests of the browser and returns the information required by the user to the browser. The rest of the work, such as data request, processing, result return, dynamic web page generation, access to the database, and execution of application programs, are all done by the Web Server. As Windows embeds browser technology inside the operating system, this structure has become the preferred architecture for today's application software. Obviously the B / S structure application program is a very big progress compared with the traditional C / S structure application program.
The main characteristics of the B / S structure are strong distribution, easy maintenance, simple development and strong sharing, and low total cost of ownership. However, data security problems, excessive requirements on the server, slow data transmission speed, and significantly reduced personalized features of the software are all obvious, and it is difficult to achieve the special functional requirements under the traditional mode. For example, it is difficult and inconvenient to input a large amount of data or respond to reports through a browser, and to print out specific reports. In addition, there are greater difficulties in implementing complex application configurations. Although AcTIveX, Java and other technologies can be used to develop more complex applications, relative to the development of a series of very mature C / S application tools, the development of these technologies is complex, and there are no fully mature technical tools for use.
2 Analysis and comparison of C / S structure and B / S structure
2.1 Different hardware environments
C / S is established on the basis of local area network and provides connection and data exchange services through dedicated servers. The users handled are not only fixed, but also in the same area, requiring the same operating system. B / S is built on the basis of wide area network, and the information is managed by itself. It has a stronger adaptability range than C / S. Generally, as long as there is an operating system and a browser. Minimal relationship with operating system platform. For the unknowable user base.
2.2 Different structure
C / S software generally adopts a two-layer structure, while B / S adopts a three-layer structure:
The difference between these two structures is that the client in the two-layer structure participates in the calculation, while the client in the three-layer structure does not participate in the calculation, but simply receives the user's request and displays the final result. Since the client in the three-tier structure does not need to participate in the calculation, the computer and computer configuration requirements of the client are relatively low. Although BlS adopts a logical three-layer structure, the physical network structure is still the original Ethernet or ring network. In this way, the communication between the first layer and the second layer structure and the communication between the second layer and the third layer structure all need to occupy the same network line, and the network traffic is large. C / S has only a two-layer structure, and the network traffic only includes the traffic between Client and Server, and the network traffic is low. Therefore, the ability of C / S to process a large amount of information is unmatched by B / S.
2.3 Different processing modes
Compared with C / S, the processing mode of B / S greatly simplifies the client, as long as the operating system, network protocol software and browser are installed, then the client becomes a thin client, and the server concentrates all Application logic.
2.4 Different component reuse
In terms of reusability of components, the C / S program has a low reusability when considered as a whole. BlS corresponds to multiple structures, requiring components to have relatively independent functions and good reusability.
2.5 Different system maintenance
System maintenance is the most expensive part of the software life cycle. Due to its own integrity, the C / S program must examine and deal with the problems as a whole. With the B / S structure, the client does not need to be installed and maintained. The B / S structure only changes individual components in terms of component composition, and development, maintenance and other work are concentrated on the server side. When an upgrade is required, only the software on the server side needs to be updated without replacing the client software, and a seamless upgrade of the system is achieved. This reduces the cost and workload of system maintenance and upgrades, and greatly reduces the user's total cost of ownership (TCO).
2.6 Different safety requirements
Because C / S adopts a paired point-to-point structure mode and adopts a network protocol that is suitable for local area networks and has better security (such as NT's NetBEUI protocol), security can be better guaranteed. C / S generally faces a relatively fixed user group, and the program pays more attention to the process. It can perform multi-level verification of permissions, provide a more secure access mode, and have strong control over information security. It is appropriate to use C / S structure for general highly confidential information systems. B / S adopts an open structural model of point-to-multipoint and multi-point-to-multipoint, and adopts TCP / IP, an open protocol applied to Internet. Its security can only rely on managing passwords on data servers Database to guarantee. Therefore, B / S has higher requirements on security and access speed than C / S. However, these key security issues in the Internet technology are far from being resolved.
2.7 Different speeds
Because C / S is one layer less than B / S in logical structure, for the same task, C / S can always complete faster than B / S. Make C / S more conducive to processing large amounts of data.
2.8 Interactivity is different from information flow
Strong interactivity is an inherent advantage of C / S. In C / S, the client has a complete set of applications, with powerful functions in error prompts, online help, etc., and can freely switch between subprograms. Although B / S provides certain interactive capabilities by javascript and VBScript, it is too limited compared to C / S's set of client applications. The information flow of C / S is single, while B / S can process information such as BB, BC, BG, etc. and has a change of flow direction.
3 Architecture based on the combination of B / S structure and C / S structure
In summary, we can see that the two technologies B / S and C / S have their own advantages and disadvantages.
C / S technology is the mainstream development technology 20 years ago, it is mainly limited to the needs of internal LAN. Therefore, it lacks some characteristics as an application platform, and it is difficult to extend to the environment such as the Internet, and requires developers to deal with system level issues such as transaction management, message queue, data replication and synchronization, and communication security. This puts higher demands on application developers, and forces application developers to devote a lot of energy to solve problems outside the application. This makes the maintenance, transplantation and interoperability of application programs complicated, which has become a major defect of C / S.
However, compared with the B / S structure, the development history of C / S technology is more "long". From the perspective of technology maturity, software design, and the mastery of developers, C / S technology is more mature and reliable. In some cases, using 100% B / S will cause problems such as slow system response speed, large server overhead, high communication bandwidth requirements, poor security, and increased total investment. Moreover, for some complex applications, there is currently no suitable way for B / S development. 
It has become an inevitable trend to objectively analyze the advantages and disadvantages of C / S and B / S, and to establish a network architecture combining C / S and B / S structures. In the actual development and planning of the system, it must be targeted to be able to build a suitable information system.
The following uses the school student management system as an example to illustrate this design method. The system adopts B / S + C / S architecture, combines ASP technology, and applies component technology COM + and AcTIveX technology to the server and client respectively. The realization of the system is mainly divided into three parts: ASP page, COM + component and database, which is a three-layer structure. The presentation layer is composed of ASP pages to realize WEB page display and call COM + components. Business logic and data access are composed of a set of COM + components implemented with VC. In order to facilitate maintenance, upgrade and implementation of distributed applications, during the implementation process, the business logic layer and the data access layer are separated. ASP pages do not directly call the data access layer, but call the database through the business logic layer. Some functional interfaces that need to be processed by WEB and satisfy most visitor requests adopt B / S structure. For example, instructors can query various related information of the students in the class they teach through the browser; school administrators Teachers and other information for management and maintenance and query statistics; leadership can query and make decisions through the browser data. This client is more flexible. The functions that only a few people use in the background use C / S structure, such as database management and maintenance interface. In this way, the advantages of various modes can be fully utilized-avoiding the disadvantages of B / S structure in terms of security, confidentiality and response speed, and the disadvantages of C / S structure in maintenance and flexibility. The realization of COM + can be divided into three steps: the design of COM + components, the generation and programming of COM + applications. The COM + component is located in the WEB application, and the client sends a request to the WEB SERVER. WEB SERVER transmits the request to the WEB application. The WEB application transmits the data request to the database server, and the database server returns the data to the WEB application. Then the data is transferred to the client by WEB SERVER. For some of the more difficult functions to achieve by embedding the AcTIveX control in the page.
The advantages of using this structure are:
(1) Give full play to the advantages of B / S and C / S architecture and make up for the deficiencies of the two. Taking full account of the interests of users, and ensuring the convenient operation of browsing inquiries, it also makes the system simple to update, simple and flexible to maintain, and easy to operate.
(2) Information release adopts B / S structure, keeping the advantages of thin client. The software loaded into the client can use a unified WWW browser. And since the WWW browser and network integrated server are based on industry standards, they can work on all platforms.
(3) The database uses C / S structure and connects via ODBC / JDBC. This part only involves system maintenance, data update, etc. There are no shortcomings such as a large client maintenance workload brought by completely adopting C / S structure. And the client can construct very complex applications, friendly and flexible interface, easy to operate, can solve many of the inherent shortcomings of B / S.
(4) For the application based on the original C / S architecture, it is very easy to upgrade to this architecture by retaining the WWW interface for publishing, and retain some of the original subsystems. This makes full use of existing system resources.
(5) By embedding ActiveX controls in the browser, you can implement functions that are not possible or difficult to implement in the browser. For example, respond to reports through a browser.
(6) Divide the server into two parts: WEB server and WEB application program. The WEB application uses component technology to implement the logical part of the three-tier architecture to achieve the purpose of encapsulation.
B / S structure and C / S structure have their own advantages and disadvantages. How to combine B / S and C / S development system is a common concern in the development of MIS system. In the application process, we should combine the actual situation, and select and construct the system according to the actual situation, so as to develop an efficient and safe application system.
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