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Three Tier Model
                                                          Three Tier Architecture










                                         Client                   Server               Database

              The three-tier web architecture consists of the presentation tier, or user interface; the application tier, where data is
              processed; and the data tier, where the data associated with the application is stored and managed.
              As each tier runs on its own infrastructure, three-tier architecture has the advantage of allowing each tier to be created
              in parallel by a distinct development team and updated or scaled as needed without affecting the other tiers.
              In general, server-side and client-side data processing are distinguished. Dynamic websites are defined by the notion
              that content can be modified on the client-side without requiring fresh server-client communication. Scripts impact
              client behaviour, eliminating the need for asynchronous data transfer. Modified material is stored on the database
              server via the application server on the server-side. This could be a virtual server that replicates a physical server.
              Three-tier structures can be implemented using a variety of computer languages and frameworks as follows:


              Ð ÐHypertext Preprocessor (PHP)
              Ð ÐCommon Gateway Interface (CGI)
               ÐJavaServer Pages (JSP)
              Ð
              Ð ÐAsynchronous JavaScript and XML (AJAX)
              Ð ÐJavaScript Object Notation (JSON)

              Ð ÐJava applets, JavaScript, and VBScript (client-side technologies)
              Service-Oriented Architecture (SOA)

              The internet is being utilised to connect internationally spread IT structures. The client-server architecture is no longer
              applicable to modern IT and online applications. Business operations can be automated with SOAs by the systems
              involved, communicating with one another and completing certain tasks, partly without human interaction. Online
              banking, e-commerce, e-learning, online markets, and business intelligence applications are just a few examples.
              N-tier architectures are what they’re called, and they’ve mostly been used in the commercial world so far.

                                                                                            Remote
                                                                                            Service
                                                                           Middle
                                                                           Tier 1
                                                       Web
                                   Client    WAF       Tier                         Cache
                                                                                             Data
                                                                                             Tier
                                                                           Middle
                                                               Messaging
                                                                           Tier 2


              Different architectures have a wide range of consequences. With hundreds of protocols, programming and scripting
              languages, frameworks, and interfaces, websites and online services are developing at a rate that not even developers
              can keep up with. Websites become more interactive, data can be transmitted more quickly, and services can readily
              communicate with one another. Web architectures are growing increasingly complex, and many distinct techniques
              exist at the same time, from the developer’s perspective.

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