计算机专业b-s模式--外文翻译-外文文献-英文文献-中英对照.doc

外文翻译
ENGLISHE：
Develop Web application program using ASP the architecture that must first establish Web application. Now in application frequently with to have two: The architecture of C/S and the architecture of B/S.
Client/server and customer end / server hold the architecture of C/S.
The customer / server structure of two floor.
Customer / server ( Client/Server ) model is a kind of good software architecture, it is the one of best application pattern of network. From technology, see that it is a logic concept, denote will a application many tasks of decomposing difference carry out , common completion is entire to apply the function of task. On each network main computer of web site, resource ( hardware, software and data ) divide into step, is not balanced, under customer / server structure, without the client computer of resource through sending request to the server that has resource , get resource request, so meet the resource distribution in network not balancedness. With this kind of structure, can synthesize various computers to cooperate with work, let it each can, realize the scale for the system of computer optimization ( Rightsizing ) with scale reduce to melt ( Downsizing ). Picture is as follows:

It is most of to divide into computer network application into two, in which the resource and function that part supports many users to share , it is realized by server; Another part faces every user , is realized by client computer, also namely, client computer is usual to carry out proscenium function , realizes man-machine interaction through user interface , or is the application program of specific conducted user. And server usually carries out the function of backstage supporter , manages the outside request concerning seting up, accepting and replying user that shared. For a computer, it can have double function , is being certain and momentary to carve to act as server , and again becomes client computer in another time.
Customer / server type computer divide into two kinds, one side who offers service is called as server , asks one side of service to be called as customer. To be able to offer service, server one side must have certain hardware and corresponding server software; Also, customer one side must also have certain hardware and corresponding customer software.
There must be a agreement between server and customer both sides communicate according to this agreement.
Apply customer / server model in Internet service , the relation between customer and server is not immutable. Some Internet node offers service on the one hand , also gets service on the other hand from other node; It is even in one time dialogue course, mutual role also exchanges probably. As in carry out file transmission , if be called as one side who offers file server, is called as one side who gets file customer, when using get or mget order since another node takes file, can think that what self use and it is client computer , is using put or mput order to another node dispatch file can again think the machine that used self is server.
Multilayer customer / server structure
Along with the development of enterprise application, recently, have again arisen a kind of new multilayer architecture, it applies customer end to divide into two minutes: Customer application and server apply. Customer application is the part of original customer application , is another and partial to have been transfered to server to apply. New customer application takes the responsibility for user interface and simple regular business logic and new server application resident core , changeable business logic. Therefore its structure has become new ( Client application + Server application )/Server structure. Following picture shows:

This kind of structure has solved traditional Client/Server can expand problem, have reduced customer end business logic , and have reduced the requirement of customer end for hardware. At the same time because of a lot of business logic concentrations have gone to unitary application server on, the maintenance work of application system had been also concentrated together, have eliminated the problem in the traditional structure of Client/Server that software distributes. This kind of structure is called as the architecture of B/S.
Browser/Server and browser / server hold the architecture of B/S. On essence, Browser/Server is also a kind of structure of Client/Server, it is a kind of from the traditional two levels of structural development of Client/Server come to the three-layer structural special case of Client/Server that applied on Web.
In the system of Browser/Server, user can pass through browser to a lot of servers that spread on network to send request. The structure of Browser/Server is maximum to have simplified the work of client computer, on client computer, need to install and deploy few customer end software only , server will bear more work, for database visit and apply program carry out will in server finish.
Under the three-layer architecture of Browser/Server, express layer ( Presentatioon ) , function layer ( Business Logic ) , data layer ( Data Service ) have been cut the unit of 3 relative independences:
It is the first layer of to express layer: Web browser.
In expressing layer contain system show logic, locate in customer end. It's task is to suggest by Web browser to the certain a Web server on network that service is asked , after verifying for user identity, Web server delivers needed homepage with HTTP agreement to customer end, client computer accept the homepage file that passed , and show it in Web browser on.
Second layer function layer: Have the Web server of the application function of program extension.
In function layer contain the systematic handling of general affairs logic, locate in Web server end. It's task is the request concerning accepting user , need to be first conducted and corresponding to expand application program and database to carry out connection , passes through the waies such as SQL to database server to put forward data handling to apply for, then etc. database server the result of handling data submit to Web server, deliver again by Web server to return customer end.
The number of plies of 3th according to layer: Database server.
In data layer contain systematic data handling logic, locate in database server end. It's task is to accept the request that Web server controls for database, realization is inquired and modified for database , update etc. function, submit operation result to Web server.
Careful analysis is been easy to see , the architecture of Browser/Server of three-layer is the handling of general affairs of the two levels of structure of Client/Server logic modular from the task of client computer in split , from the first floor of individual composition bear the pressure of its task and such client computer have alleviated greatly, distribute load balancedly and have given Web server, so from the structural change of Client/server of original two floor the structure of Browser/Server of three-layer. This kind of three-layer architecture following picture shows.
This kind of structure not only client computer from heavy burden and the requirement of performance that rises continuously for it in liberation come out , also defend technology people from heavy maintenance upgrading work in free oneself. Since client computer handles general affairs , logic partial minutes have given function server, make client computer right off " slender " a lot of, do not take the responsibility for handling complex calculation and data again visit etc. crucial general affairs, is responsible to show part, so, maintenance people do not rush about again for the maintenance work of program between every client computer, and put major energy in the program on function server update work. Between this kind of three-layer structural layer and layer, the mutually independent change of any first floor does not affect the function of other layer. It has changed the defect of the two levels of architecture of Client/Server of tradition from foundation, it is the transform with deep once in application systematic architecture.
The contrast of two architectures
The architecture of Browser/Server and the architecture of Client/Server compare with all advantages that not only have the architecture of Client/Server and also have the architecture of Clinet/Server the unique advantage that place does not have:
Open standard: The standard adopted by Client/Server only in department unification for but, it's application is often for special purpose.
It is lower to develop and defend cost: It need to be implemented on all client computers that the application of Client/Server must develop the customer end software for special purpose, no matter installation and disposition escalate still, have wasted manpower and material resources maximumly. The application of Browser/Server need in customer end have general browser , defend and escalate to work in server end go on , need not carry out any change as customer holds , have reduced the cost of development and maintenance so greatly.
It is simple to use , interface friendly: The interface of the user of Client/Server is decided by customer end software, interface and the method of its use are not identical each, per popularize a system of Client/Server ask user study from the beginning, is hard to use. The interface of the user of Browser/Server is unified on browser, browser is easy to use , interface friendly, must not study use again other software, the use of a Lao Yong Yi that has solved user problem.
Customer end detumescence: The customer end of Client/Server has the function that shows and handles data , as the requirement of customer end is a client computer " it is fat " very high. The customer of Browser/Server holds the access that not takes the responsibility for database again and the etc. task of complex data calculation, need it only show , the powerful role that has played server fully is so large to have reduced the requirement for customer end, customer end become very " thin ".
System is flexible: The 3 minutes of the system of Client/Server, in modular, have the part that need to change to want relation to the change of other modular, make system very difficult upgrading. The 3 minutes of the system of Browser/Server modular relative independence, in which a part of modular change, other modular does not get influence, it is very easy that system improve to become, and can form the system with much better performance with the product of different manufacturer.
Ensure systematic safety: In the system of Client/Server, directly join with database server because of client computer, user can very easily change the data on server, can not guarantee systematic safety. The system of Browser/Server has increased a level of Web server between client computer and database server , makes two not to be directly linked again, client computer can not be directly controled for database, prevent user efficiently invade illegally.
The architecture of Browser/Server of three-layer has the advantage that a lot of traditional architectures of Client/Server does not have , and is close to have combined the technology of Internet/Intranet, is that the tendency of technical development tends to , it application system tape into one brand-new develop times. From this us option the configuration of B/S the architecture that develops as system.
what are C/S with B/S
For " C/S " with the technology of " B/S " develop change know , first,must make it clear that 3 problems.
( 1 ) What is the structure of C/S.
C/S ( Client/Server ) structure, the server structure and client computer that all know well. It is software systematic architecture, through it can hold hardware environment fully using two advantage, realize task reasonable distribution to Client end and Server end , have reduced systematic communication expense. Now, the most systems of application software are the two levels of structure of the form of Client/Server , are developing to the Web application of distribution type since current software application is systematic, Web and the application of Client/Server can carry out same business handling , apply different modular to share logic assembly; Therefore it is systematic that built-in and external user can visit new and existing application , through the logic in existing application system, can expand new application system. This is also present application system develop direction.
Traditional C ／ S architecture though adopting is open pattern, but this is the openness that system develops a level , in specific application no matter Client end or Server end the software that need to still specify support. Because of the software software that need to develop different edition according to the different system of operating system that can not offer the structure of C/S and the open environment of user genuine expectation , besides, the renovation of product is very rapid, is nearly impossible to already meet the 100 computer above users of local area network at the same time use. Price has low efficiency high. If my courtyard uses , Shanghai exceed the orchid company's management software " statistics of law case" is typical C ／ S architecture management software.
( 2 ) What is the structure of B/S.
B/S ( Browser/Server ) structure browser and server structure. It is along with the technology of Internet spring up , it is for the structure of improvement or a kind of change of the structure of C/S. Under this kind of structure, user working interface is to realize through WWW browser, lose the logic of general affairs very much in front( Browser) realization, but the major logic of general affairs in server end( Server) realization, form the three-layer claimed 3-tier structure. So, have simplified customer end computer load greatly , have alleviated system to defend workload and the cost with upgrading , have reduced the overall cost of user ( TCO ). With present technology see , local area network the network application that establishes the structure of B/S , and under the pattern of Internet/Intranet, database application is easy to hold relatively , cost also is lower. It is that oneness goes to the development of position , can realize different people, never same place, with difference receive the way of entering ( for example LAN, WAN, Internet/Intranet etc.) visit and operate common database; It can protect data platform efficiently with management visit limits of authority, server database is also safe. Now in my courtyard, net ( Intranet ) , outer net ( Internet ) with Beijing eastern clear big company " law case and the management software of official business " is the structural management software of B/S , policemen each work