《计算机与网络》PPT课件.ppt

SSD1 IntroductiontoInformationSystems Unit1 UsingtheWeb WangLiweiliwei wang ISS WuhanUniversity 2 TheWorldWideWeb IntroducetheWorldWideWebanditsworkings UsingtheWebWhat sintheWeb IntroductiontoHTMLFormsandServlets 3 1 1UsingtheWeb SurfingtheWebYourWebPagesClients Servers andURLsSearchingtheWebCommerceontheWebSomeEthicalConsiderations 4 SurfingtheWeb InternetWorldWideWebSurfingInternetServiceProvider ISP 5 Internet Internetisacomputernetworkthatconnectsmillionsofcomputersacrossanumberofcountries ThereisnocentralauthoritythatcontrolstheInternet differentorganizationsowndifferentpiecesofit 6 HistoryoftheInternet TheInternetcomesfromARPAnetcreatedbytheU S DefenseAdvancedInternetResearchProjectsAgency DARPA in1969 In1983 ARPAnetsplitintoARPAnetandmilitaryMILNET theyarereferredtoastheearlyInternetbackbonenetwork ThisyearinJanuary TransportControlProtocol InternetProtocol TCP IP officiallybecomethestandardprotocolforARPAnet 7 HistoryoftheInternet In1985 theNationalScienceFoundation NSF providedhugeamountsofmoneytobuildthefivesupercomputingcenters In1987 NSFestablisheditsowncomputernetworkNSFnetbasedonTCP IPprotocol In1990 NSFnetcompletelyreplacedtheARPAnetandbecomesInternetbackbone In1995 theInternetbeganlarge scalecommercialapplicationinthefield 8 CharacteristicsoftheInternet AnetworkofnetworksInformativeandresourcefulFastandconvenientEndlessonlineactivitiesInformationdiversity 9 ThemainInternetservice WWW WorldWideWeb WWWisusedforInformationcollectionandreleasingUserscanmanipulatethemousetofindhypertext hypermediadocumentprovidedbyallsitesbuiltonWWWservers 10 ThemainInternetservice WWW 11 ThemainInternetservice E mail Electronicmail E mailwasoneofthefirstusesoftheInternetandisstillthemostpopularuse E mailsystemusesSMTPprotocoltosende mailfromtheuser scomputertothemailserver E mailsystemusesthePOP3protocoltotransfersthemessagefromthemailservertotheuser E mailmessagescansendnon textfiles suchasgraphicimagesandsoundfiles asattachmentssentinbinarystreams 12 ThemainInternetservice E mail 13 ThemainInternetservice FTP FileTransferProtocol FTPistheprimarymeansofgettingfilesfromtheremotehostontheInternetWhenthefileissentfromclienttoaremotehost knownasthe fileupload Upload otherwise knownasthe FileDownload Download Transferredfilescanbetextfiles executablefiles soundfiles imagefiles datacompressionfiles 14 ThemainInternetservice TelnetTelnetisanetworkprotocolusedontheInternetorlocalareanetworkstoprovideabidirectionalinteractivecommunicationsfacilityviaa terminalconnection Userlogsontoanotherhostviaavirtualterminalconnectionandenjoystheresourcesandservicesprovidedbythehost 15 WorldWideWeb WhatisWWW WWW or theweb referstothatportionofthecomputersontheInternetthatcancommunicatewitheachotherusingacomputer networkprotocolcalledHTTP WWWisasystemofinterlinkedhypertextdocumentswithclient servermodel 16 WorldWideWeb ThreeelementsofWWWUnifiedresourcenaming UniformResourceLocator URL Unifiedresourceaccessing HypertextTransferProtocol HTTP AllbrowsersuseHTTPtorequestandreceiveWebpagesfromothercomputers UnifiedinformationOrganization HyperTextMarkupLanguage HTML 17 WorldWideWeb CharacteristicsofWWWDistributedinformationresourcesUnifieduserinterfaceWebbrowser IE MS Safari Apple Chrome Google Firefox Mozilla SupportsavarietyofmediaresourcesText Photo Voice Video SearchingandpublishinginformationClient ServermodelWebBrower WebServer 18 Surfing Tosurfwebeffectively efficientsearchrequired Webpage Websiterefertothelocationsonwebthatcanbevisitedthroughabrowser Twomajorareasofcontrolontheweb namingofwebsiterulesofInternetServiceProvider ISP Noorganizationresponsibleforcontentontheweb 19 Othernotesontheweb WebSecurity oneofthemajorareasofconcernforwebtransactionsandpersonalinformationhostedontheweb CaveatEmptor and BuyerBeware importantrulesforwebsurfers SearchEnginesusedtosearchanyinformaiononthewebusingkeywords 20 InternetServiceProvider ISP AnISPisanyoneofanumberofcompaniesthatenablepeoplenotonlytoconnecttotheInternetandsurftheWebbutalsotopublishWebpages IAP InternetAccessProvider ICP InternetContentProvider 21 YourWebPages Reasonable PersonPrinciple Whenhostingawebsite pagesshouldbemaintainedforotherstoviewInformationonthepagesshouldbecorrectandup to date Presentingemailinformationonwebpageimpliesbeingresponsivetoemailsbysurfers Displayingpersonalinformationonwebpagesnotagoodidea 22 Clients Servers andURLs Clients Anapplicationthatrequestsinformationfromaserverapplicationoraskstheservertoperformsometask Eg WebBrowser Servers Applicationsthatrunonrelativelymorepowerfulcomputers toserviceconcurrentrequestsfromanumberofclients 23 Clients Servers andURLs Clientasksfortheresourceanddealswithit Serverprovidetheresource Thebrowserisconsideredaclient Thesitethatsuppliestheinformationisconsideredaserver 24 Clients Servers andURLs ServersMicrosoftInternetInformationServer IIS ApacheServerIBMWebsphere 25 URLs UniformResourceLocatornamingschemeProvidesuserwithawaytoaccessWebresourcesusingauniformmeansforaddressingresources protocol nameofmachine nameofresource 26 27 URLs Cont protocol nameofmachine nameofresource Eg ftp 28 Clients Servers andURLs Client Server C S Disadvantage fatclientsBrowser Server B S BelongtoC SAdvantage Clientiswebbrowser 29 BasicModel Serverlocatestheresource 30 QuestionsaboutC S GiventhedescriptionofWebserversabove whatlimitationscanyouseewiththisC Smodel Intheabovemodel cantheclientreceivepersonalizedinformation InyourownexplorationsoftheWorldWideWeb whatbehaviorshaveyouseenthatthemodelabovedoesnotaccountfor 31 BeyondtheBasicModel Serverexecutesauxiliaryapplications 32 Browsingvs Searching Browsing UnfocusedrandompassingfromlinktolinkaroundthewebSearching Usingasearchenginetolocatearesourceontheweb Searchingmayeventuallyrunintobrowsing SearchEngine Aprogramthatimplementsdifferentsearchmechanisms likeindexingsitesanditspages 33 SearchingtheWeb BrowsingandsearchingSearchengineisaprogramthatallowsonetosearchforkeywordsinfilesatoneormoreInternetsites Google Excite Lycos AltaVista 34 TypesofSearchSites SearchEngine FeaturedSitesthatmaintainindexesordatabasesoftheaddressesofvirtuallyallofthepagesanddocumentsontheWeb Theseindexesordatabasesmaintainedregularlyusing spiders foraddressesofnewdocumentsthatbecomeavailableonthenet Eg google 35 TypesofSearchSites WebDirectory FeaturedInformationorganizedintocategoriesandsubcategories mostlybasedonhumaneffort Onlyafractionofnetinwebdirectories andownersofrelevantWebsitesresponsibleforinclusionoftheirsites Eg Yahoo 36 Howtosearch UseasearchsiteTypekeywordsofyoursearchintothesearchengineSearch Usethehelpinformationofferedbyeachsearchengine 37 Asearchsample results 38 Asearchsample results 39 Commerceontheweb InternetServiceProvidersSellaccesstotheinternetintermsoflogonservice emailservice webpublishingEstablishingandmaintainingwebpresencedonethroughISPscanbeexpensive PricebasedonnumberofhitsthatcanbehandledAdvertisingAwayforsearchenginecompaniestomakemoneybydisplaying visualclutter Adsdisplayedbasedonwhatisbeingsearchedfor andcanbelinked 40 WebCommerce CommercialTransactionsGrowingpercentageofInternetcommercethatinclu