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Siena CSIS 401 - Web Application Architecture

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Slide 1Client Server ModelServer Applications (Software)Client Applications (Software)Client-Server AdvantagesClassic Example: Early Banking SystemsClassic Example: Early Banking SystemsClassic Example: Early Banking Systems3-Tiered Systems3-Tiered SystemAdvantage of 3-Tier SystemsInternet vs. WWWWWW – Ultimate Client-Server SystemFirst Web ApplicationsFirst Web ApplicationsFirst Web ApplicationsFirst Major ImprovementColdFusionColdFusion ExampleColdFusionProblems with ColdFusionAlternative’s to ColdFusionWWW – Ultimate Client-Server SystemWeb Application ArchitectureBird Book pp 1-14Client Server ModelServer Applications (Software)Management and maintenance of Data includingUser login dataApplication dataData processingCentralized Access via LoginClient Applications (Software)Provides user interfaceStores some settingsCan do some data processingLittle to no application data storageSame view of data no matter where you loginClient-Server AdvantagesCentralized Data StorageNo data redundancy (no duplication of data)Reduces data dependenciesIf data is stored on each user’s system and each system is different than data depends on how the user system is designedData can not be shared easily if such dependencies existClassic Example: Early Banking SystemsNetwork: Local Area Network (LAN) covering local office branch.Server: Mainframe-like server “in the back” running custom banking systemClient: Windows PC with client interface for each bank teller.Data is the same no matter what teller you go to.Data is NOT the same if you go to another branch unless servers exchanged some data at night.Classic Example: Early Banking SystemsThe Obvious Future:Change the LAN to a wide area network covering all the branches.Get rid of the individual servers at each branchHave clients connect to central server where ALL the banking data is stored.Classic Example: Early Banking SystemsThe Obvious Problems:Large banks could have thousands of tellers connecting to the central server.Combining data from all branches requires severs with lots of storage capacity.Branch data could be stored in different formats.Lack of Standardization.3-Tiered Systems3-Tiered SystemDatabase Tier (Database Server)Data storage and low level data manipulationServer Tier (Application Server)Manage client connections and data processingClient Tier (Client Software installed locally)User interface and some data processingAdvantage of 3-Tier SystemsCentral Database Server accessed by multiple Application ServersIn turn, each Application Server could independently manage thousands of usersDatabase Server is specially designed to do its jobDatabase Operations: Update, Insert, Remove, etc.Lots of disk storage and memory neededApplication Servers can be added to support more users or DIFFERENT APPLICATIONSServer Operations: Complex application-dependent computationsLots of processor power neededInternet vs. WWWInternet is the infrastructure that makes the WWW work.Packet SwitchingTCP/IP ProtocolPhysical InfrastructureFiber-optics lines, wiresSatellites, Cable ModemsRouters, Hubs, Network Cards, WiFi systems, etc.WWW is just one of many “virtual networks” built on the Internet.Websites: http, https, etc.Email: pop, imap, etc.Other systems: ftp, instant messaging, etc.Note: Even to this day companies have “private virtual networks” that use the Internet, but are proprietary, locked-down.WWW – Ultimate Client-Server SystemAlready StandardizedBuilt on the Widest Area Network you could imagine, i.e., The InternetStandardized Clients that are free to useIE, Firefox, Safari, etc.Lots of Servers already in placeApache, Windows Server (IIS), etc.Database ServersUmm, this was initially missingFirst Web Applications1993 – Rob McCool proposed a framework called CGI (Common Gateway Interface)Data passed from a web browser to the server GET - passed via URL variablesPOST - passed via HTML forms Web server daemon (httpd) could then make remote system callsExampleWeb server could run a C++ program and write the output to public HTML folderWeb server would send response back with location of the output.First Web ApplicationsUsing CGI, web server could run C++ programsPerl ProgramsFortran ProgramsC++ has library functions that allow you to connect to a number of different databases:OracleSybaseDB2First Web ApplicationsProblem:To develop web applications you need to knowExactly how your server is configuredHTML formsGET and POST conventionsC++ database librariesSQL languageGetting all these things to work together is a pain in the ***.First Major Improvement1995 – JJ Allaire developed “a hack” that allowed a web servers to communicate with other systems, namely a database system.Key: Instead of using “a middle-man” C++, Perl, Java, etc.Developer could directly add code to the their web pagesUsing a special Markup Language, this code could be embedded in any web page.Worked seamlessly with HTML formsServer process code directlyColdFusionJJ Allaire went on to form a company Allaire which developed his idea into a product called ColdFusionColdFusion Markup Language (CFML)ColdFusion Server (addon to popular Web Servers like Apache, Microsoft’s IIS).Notes:Allaire was bought by Macromedia 2001.Macromedia was bought by Adobe in 2005.ColdFusion Example<cfset droplist = "colorlight,colordark"><cfoutput> <form action="#cgi.script_name#" method="get" name="choosecolors" id="choosecolors"> <fieldset> <legend>Customize Site</legend> <label for="colorlight">light color</label> <input type="text" name="colorlight" id="colorlight" size="10" value="#url.colorlight#" /><br /> <label for="colordark">dark color</label> <input type="text" name="colordark" id="colordark" size="10" value="#url.colordark#" /> #getTokensMinusArg('inputs',droplist)# <input type="submit" name="changecolors" value="Reload" /> </fieldset> </form></cfoutput>ColdFusionThe term Cold Fusion refers to a nuclear reaction that can occur at room temperatureIn the 1980’s it was believed that Cold Fusion was a physical possibility.If Cold Fusion could be achieved then almost unlimited power could be generated by a reaction you could perform in your own kitchen. JJ


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