chapter 2 the internet and world wide 4. the world wide web 课件

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1、CHAPTER2TheInternetandWorldWideWebTheWorldWideWebWWWBackground1989-1990–TimBerners-LeeinventstheWorldWideWebatCERNMeansfortransferringtextandgraphicssimultaneouslyClient/ServerdatatransferprotocolCommunicationviaapplicationlevelprotocolSystemranontopofstandardnetworkinginfrastr

2、uctureTextmarkuplanguageNotinventedbyBernes-LeeSimpleandeasytouseRequiresaclientapplicationtorendertext/graphicsTheHistoryofWWW1994–MarkAndreeseninventsMOSAICatNationalCenterforSuperComputingApplications(NCSA)FirstgraphicalbrowserInternet’sfirst“killerapp”FreelydistributedBecam

3、eNetscapeInc.1995(approx.)–WebtrafficbecomesdominantExponentialgrowthE-commerceWebinfrastructurecompaniesWorldWideWebConsortiumReference:“WebProtocolsandPractice”,KrishnamurthyandRexfordWWWComponentsStructuralComponentsClients/browsers–todominantimplementationsServers–runonsoph

4、isticatedhardwareCaches–manyinterestingimplementationsInternet–theglobalinfrastructurewhichfacilitatesdatatransferSemanticComponentsHyperTextTransferProtocol(HTTP)HyperTextMarkupLanguage(HTML)eXtensibleMarkupLanguage(XML)UniformResourceIdentifiers(URIs)QuickAside–Webserveruse6W

5、WWStructureClientsusebrowserapplicationtosendURIsviaHTTPtoserversrequestingaWebpageWebpagesconstructedusingHTML(orothermarkuplanguage)andconsistoftext,graphics,soundsplusembeddedfilesServers(orcaches)respondwithrequestedWebpageOrwitherrormessageClient’sbrowserrendersWebpageretu

6、rnedbyserverPageiswrittenusingHyperTextMarkupLanguage(HTML)Displayingtext,graphicsandsoundinbrowserWritingdataaswellTheentiresystemrunsoverstandardnetworkingprotocols(TCP/IP,DNS,…)7UniformResourceIdentifiersWebresourcesneednames/identifiers–UniformResourceIdentifiers(URIs)Resou

7、rcecanresideanywhereontheInternetURIsareasomewhatabstractnotionApointertoaresourcetowhichrequestmethodscanbeappliedtogeneratepotentiallydifferentresponsesArequestmethodise.g.fetchingorchangingtheobjectInstance:http://www.foo.com/index.htmlProtocol,server,resourceMostpopularform

8、ofaURIistheUniformResourceLocator(URL)Differencesbetwe