电子商务概论知识PPT课件

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1、电子商务概论知识 Cengage Learning 20151Learning ObjectivesIn this chapter,you will learn:About the origin,growth,and current structure of the InternetHow packet-switched networks are combined to form the InternetHow Internet,e-mail,and Web protocols workAbout Internet addressing and how Web domain names are

2、 constructed Cengage Learning 20152 2Learning Objectives(contd.)About the history and use of markup languages on the WebHow HTML tags and links workAbout technologies people and businesses use to connect to the InternetAbout Internet2 and the Semantic Web Cengage Learning 20153 3IntroductionA growin

3、g number of Internet users are using smartphone or tabletSmartphones are typically only the access method in developing countriesHistory of Internet-capable mobile phonesFirst introduced in late-1990sSlow,unreliable service,no keyboards2001:Treo,Blackberry introduced2009:All major phone manufacturer

4、s had products2011-2013:Lower price phones targeted developing markets Cengage Learning 20154The Internet and the World Wide WebComputer networkTechnology allowing people to connect computersInternet(capital“I)Interconnected global computer networksinternet(small“i”)Group of interconnected computer

5、networksBasic technology structureSupports networks,the Internet,and e-commerce Cengage Learning 20155 5The Internet and the World Wide Web(contd.)World Wide Web(Web)Subset of Internet computers Includes easy-to-use interfaces Cengage Learning 20156 6Origins of the InternetEarly 1960sDefense Departm

6、ent nuclear attack concernsPowerful computers(large mainframes)Leased telephone company linesSingle connectionSingle connection risk solutionCommunicate using multiple channels(packets)1969 Advanced Research Projects Agency(ARPA)Packet network connected four computersARPANET:earliest network(became

7、the Internet)Academic research use(1970s and 1980s)Cengage Learning 20157New Uses for the InternetDefense Department network:the original goalTo control weapons systems;transfer research files1970s:other usesE-mail(1972)Networking technologyRemote file transfer and computer accessMailing lists1979:U

8、senet(Users News Network)Read and post articlesNewsgroups(topic areas)Cengage Learning 20158New Uses for the Internet(contd.)Limited Internet useResearch and academic communities1979 1989Network applications improved and testedDefense Departments networking softwareGained wider academic and research

9、 institution useCommon communications network benefit recognizedSecurity problems recognized1980s:personal computer use explosionAcademic and research networks merged Cengage Learning 20159Commercial Use of the InternetNational Science Foundation(NSF)Provided fundingProhibited commercial network tra

10、fficBusinesses turned to commercial e-mail providersLarger firms built networks(leased telephone lines)1989:NSF permitted two commercial e-mail services(MCI Mail and CompuServe)Commercial enterprises could send e-mailResearch,education communities sent e-mail directly to MCI Mail and CompuServe Ceng

11、age Learning 201510Growth of the Internet1991 Further easing of commercial Internet activity restrictions1995:privatization of the InternetOperations turned over to privately owned companiesInternet based on four network access points(NAPs)Network access providersSell Internet access rights directly

12、 to larger customersUse Internet service providers(ISPs)Sell to smaller firms and individuals Cengage Learning 201511Growth of the Internet(contd.)Internet hosts:directly connected computersInternet growthOne of the most significant technological and social accomplishments of last millenniumNearly e

13、very country involvedUsed by millions of peopleBillions of dollars change hands yearly Cengage Learning 201512 Cengage Learning 201513FIGURE 2-1 Growth of the Internet Cengage Learning 2015The Internet of ThingsDevices can be connected to the InternetControlled remotelyExamples:sensors,switches,opti

14、cal scannersThe Internet of thingsTerm used for these connected devicesEstimated size is nine billionProjected to reach 35 billion by 2020 Cengage Learning 201514Packet-Switched NetworksLocal area network(LAN)Network of computers located close togetherWide area networks(WANs)Networks of computers co

15、nnected over greater distancesCircuitCombination of telephone lines and closed switches connecting them to each otherCircuit switchingCentrally controlled,single-connection modelSingle electrical path between caller and receiver Cengage Learning 201515Packet-Switched Networks(contd.)Circuit switchin

16、g(contd.)Works well for telephone callsDoes not work as well for:Sending data across large WAN and interconnected network(Internet)Circuit-switched network problemConnected circuit failure Causes interrupted connection and data lossSolutionPacket switching:move data between two points Cengage Learni

17、ng 201516Packet-Switched Networks(contd.)Packet-switched networkPacketsSmall pieces labeled electronically(origin,sequence,and destination address)Travel along interconnected networks Can take different paths May arrive out of orderDestination computerCollects packetsReassembles original file or e-m

18、ail message Cengage Learning 201517Routing PacketsRouting computersDecide how best to forward each packetAlso known as routers,gateway computers,border routersGateway from LAN or WAN to InternetBorder between organization and the InternetRouting algorithmsPrograms on routing computersDetermine best

19、path for packet Cengage Learning 201518Routing Packets(contd.)Routing algorithms applied to routing table(configuration table)informationRouting table(configuration table)informationIncludes lists of connections Provides rules for:Specifying connection to use firstHandling heavy packet traffic and n

20、etwork congestionVariety of rules and standards for creating packetsHubs,switches,and bridgesDevices that move packets Cengage Learning 201519Routing Packets(contd.)Routers connect networksTranslate packets into standard formatInternet backboneRouters and telecommunication lines between Internets ma

21、in collecting points Cengage Learning 201520 Cengage Learning 201521FIGURE 2-2 Router-based architecture of the Internet Cengage Learning 2015Public and Private NetworksPublic networkPublic availabilityPrivate network Private,leased-line connectionPhysically connects intranets to one anotherLeased l

22、inePermanent telephone connection between two pointsAdvantage:securityDrawback:costScaling problem:adding companies Cengage Learning 201522Virtual Private Network(VPN)Connection via public networks and protocolsUses IP tunneling(encapsulation)systemPrivate passageway through public InternetSecure tr

23、ansmissionEncapsulationEncrypts packet content;places inside another packetIP wrapper:outer packetVPN software installed on both computers“Virtual”since connection seems permanentActually a temporary connection Cengage Learning 201523Intranets and ExtranetsIntranetAn Internet within the boundaries o

24、f the organization Interconnected private networksExtranetAn Internet that extends beyond the organization and incorporates networks of outside entitiesTechnologies(public networks,private networks,or VPNs)Independent of organizational boundaries Cengage Learning 201524Internet ProtocolsProtocol:col

25、lection of network data rules Includes transmission rules Computers must use same protocolARPANET:Network Control Protocol(NCP)Proprietary architecture(closed architecture)Manufacturer creates own protocolOpen architecture(Internet core)Uses common protocolFour key message-handling rulesContributed

26、to the Internets success Cengage Learning 201525TCP/IPRefers to the two pervasive protocols used todayTransmission Control Protocol(TCP)Controls message or file disassembly into packets before Internet transmissionControls packet reassembly into original formats at destinationsInternet Protocol(IP)S

27、pecifies addressing details for each packetLabels packet with origination and destination addresses Cengage Learning 201526IP AddressingInternet Protocol version 4(IPv4)Used since 1981 IP address32-bit number identifying computersBase 2(binary)number systemComputers use for internal calculationsDigi

28、t:0 or a 1(on or off condition)Four billion different addresses(232=4,294,967,296)Router breaks message into packetsContains source and destination IP address Cengage Learning 201527IP Addressing(contd.)Dotted decimal notationFour numbers separated by periodsIP addresses range:0.0.0.0 to 255.255.255

29、.255Byte(8-bit number)Called an octet(networking applications)Binary values:00000000 to 11111111Decimal equivalents:0 to 255Three organizations assign IP addressesARIN Whois server Returns IP address list owned by an organization Cengage Learning 201528IP Addressing(contd.)New devices creating high

30、demand for IP addressesSubnettingUse reserved private IP LAN(WAN)addresses Provides additional address spacePrivate IP addressesIP numbers not permitted on Internet packetsNetwork Address Translation(NAT)deviceConverts private IP addresses into normal IP addresses Cengage Learning 201529IP Addressin

31、g(contd.)Internet Protocol version 6(IPv6)Replaces IPv4Addresses predicted to be exhausted in 2015IPv4 and IPv6 not directly compatibleIPv6 major advantagesUses 128-bit number for addressesNumber of available addresses:34 followed by 37 zerosMore complex notation system Cengage Learning 201530Electr

32、onic Mail ProtocolsElectronic mail(e-mail)Formatted according to common set of rulesClient/server structureE-mail serverComputer devoted to e-mail handling Stores,forwards e-mail messagesE-mail client softwareReads and sends e-mailCommunicates with e-mail server softwareStandardization and rules are

33、 essential Cengage Learning 201531Electronic Mail Protocols(contd.)Two common protocolsSimple Mail Transfer Protocol(SMTP)Specifies mail message formatDescribes mail administration e-mail serverDescribes mail transmission on the InternetPost Office Protocol(POP)Sends mail to users computer;deletes f

34、rom serverSends mail to users computer;does not deleteAsks if new mail arrived Cengage Learning 201532Electronic Mail Protocols(contd.)Multipurpose Internet Mail Extensions(MIME)Set of rules for handling binary filesInteractive Mail Access Protocol(IMAP)Same basic POP functionsAdditional features th

35、at support user access to email from any computerOne disadvantage:storage of e-mail messages on e-mail server Cengage Learning 201533Web Page Request and Delivery ProtocolsWeb client computersWeb client software(Web browser software)Sends Web page file requests to other computers(Web servers)Web ser

36、ver computerWeb server softwareReceives requests from many different Web clientsClient/server architectureCombination:client computers,server computers Cengage Learning 201534Web Page Request and Delivery Protocols(contd.)Hypertext Transfer Protocol(HTTP)Internet Web page file delivery rulesWeb page

37、 request using Web browserUser types protocol nameFollowed by“/:”characters before the domain nameUniform Resource Locator(URL)Combination:protocol name,domain nameLocates resources(Web page)on another computer(Web server)Cengage Learning 201535Emergence of the World Wide WebWeb Software running on

38、Internet-connected computersGenerates network trafficWeb software:largest single traffic categoryOutpaces:e-mail,file transfers,and other data transmission trafficWeb resulted from new ways of thinking about information storage and retrievalKey technological Web elementsHypertext Graphical user inte

39、rfaces Cengage Learning 201536The Development of Hypertext1945:Vannevar Bush:The Atlantic Monthly articleVisionary ideas:future technology uses(Memex)1960s:Ted Nelson described hypertextPage-linking systemDouglas Engelbart:experimental hypertext system1987:Nelson published Literary MachinesOutlined

40、project Xanadu global system Online hypertext publishing and commerce Cengage Learning 201537The Development of Hypertext(contd.)1989:Tim Berners-LeeProposed hypertext development projectProvided data-sharing functionalityDeveloped hypertext server program codeHypertext serverStores Hypertext Markup

41、 Language(HTML)files Computers connect and read filesWeb servers(today)Hypertext servers used on the Web Cengage Learning 201538The Development of Hypertext(contd.)HTMLSet of codes(tags)attached to textDescribes relationships among text elementsHypertext link(hyperlink)Points to another location Sam

42、e or another HTML document Cengage Learning 201539Graphical Interfaces for HypertextWeb browserSoftware,e.g.,Mozilla Firefox or MS Internet Explorer Users read(browse)HTML documentsMove from one HTML document to anotherText formatted with hypertext link tags in fileGraphical user interface(GUI)Prese

43、nts program control functions,output to users,and input from usersPictures,icons,and other graphical elements Cengage Learning 201540The World Wide Web(contd.)World Wide Web:Berners-Lees name for system of hyperlinked HTML documentsQuick acceptance in scientific research community1993:first GUI prog

44、ram(Mosaic)Read HTMLUsed HTML hyperlinks for page-to-page navigationFirst Web browser widely available for personal computers Cengage Learning 201541The World Wide Web(contd.)Easy way to access Internet informationProvided by functional system of pages connected by hypertext linksProfit-making poten

45、tialNetscape Communications founded in 1994Netscape Navigator Web browser(based on Mosaic)Microsoft:Internet Explorer(most widely used)Mozilla Firefox:Netscape Navigator descendantNumber of Web sitesMore rapid growth than the Internet itself Cengage Learning 201542The World Wide Web(contd.)More than

46、 700 million Web sites300 billion Web pages2010 to 2011:number of Web sites doubled Cengage Learning 201543 Cengage Learning 201544FIGURE 2-3 Growth of the World Wide Web Cengage Learning 2015The Deep WebNon-permanent Web pages can be created based on customized response to users searchExample:searc

47、h for“online business”book on ADeep Web:information that is stored in databases and is accessible to users through Web interfacesPotentially trillions of Web pages available using deep Web Cengage Learning 201545Domain NamesDotted decimal notation difficult to rememberDomain namesSets of words assig

48、ned to specific IP addressesExample:www.sandiego.eduContains three parts separated by periodsTop-level domain(TLD):rightmost part Generic top-level domains(gTLDs)Sponsored top-level domains(sTLD)Internet Corporation for Assigned Names and Numbers(ICANN)Cengage Learning 201546 Cengage Learning 201547

49、FIGURE 2-4 Commonly used domain names Cengage Learning 2015Markup Languages and the WebText markup languageSpecifies set of tags inserted into textMarkup tags(tags)Formatting instructions Web client understandsHTMLMost commonly used Web markup languageSubset of older Generalized Markup Language(SGML

50、)Cengage Learning 201548Markup Languages and the Web(contd.)Extensible Markup Language(XML)Derived from SGMLMark up shared informationMeta languageUser creates markup elements extending XML usefulnessWorld Wide Web Consortium(W3C)Maintains Web standardsExtensible Hypertext Markup Language(XHTML)HTML

51、 version 4.0 reformulation as XML application Cengage Learning 201549 Cengage Learning 201550FIGURE 2-5 Development of markup languages Cengage Learning 2015Markup LanguagesGeneralized Markup Language(GML)Creates standard electronic document formatting stylesSGML:version of GMLAdopted by Internation

52、al Organization for Standardization(ISO)Software application independentNonproprietary;platform-independentOffers user-defined tagsNot suited to rapid Web page development;costly to maintain;requires expensive tools;hard to learn Cengage Learning 201551Hypertext Markup LanguageHypertext elementsText

53、 elements related to each otherHTMLPrevalent markup language to create Web documentsW3C HTML Working Group pageDetailed HTML versions;related topic informationHTML extensionsFeatures that work in specific Web browsersHTML version 5.0 includes audio and video features within the markup language itsel

54、f Cengage Learning 201552Hypertext Markup Language(contd.)HTML tagsInterpreted by Web browserFormat text displayEnclosed in angle brackets()Opening tag and closing tagFormat text between themClosing tagPreceded by slash within angle brackets()User may customize tag interpretationsTags:generally writ

55、ten in lowercase letters Cengage Learning 201553Hypertext Markup Language(contd.)One-sided tagsRequire opening tag onlyTwo-sided tagsOptional closing tagClosing tag position very importantOpening tag may contain one or more property modifiersFurther refine tag operationOther frequently used HTML tag

56、sGraphics and tables Cengage Learning 201554 Cengage Learning 201555FIGURE 2-6 Text marked up with HTML tags Cengage Learning 2015 Cengage Learning 201556FIGURE 2-7 Text marked up with HTML tags as it appears in a Web browser Cengage Learning 2015Hypertext Markup Language(contd.)HTML linksHyperlinks

57、 on interlinked pages form a“web”Linear hyperlink structureReads Web page in serial fashionWorks well when customer fills out form Hierarchical hyperlink structureUses an introductory page(home page,start page)linking to other pagesSite map often available for hierarchical sitesAnchor tags Cengage L

58、earning 201557 Cengage Learning 201558FIGURE 2-8 Linear vs.nonlinear paths through documents Cengage Learning 2015 Cengage Learning 201559FIGURE 2-9 Three common Web page organization structures Cengage Learning 2015Scripting Languages and Style SheetsObject tagEmbeds scripting language code on HTML

59、 pagesCascading Style Sheets(CSS)Provide more control over displayed page formatStyle sheetInstructions stored in separate fileReferenced using HTML style tagMay be included in Web pages HTML file Cengage Learning 201560Extensible Markup Language(XML)Web design toolFor presenting or maintaining info

60、rmation lists,dataIncludes data-management capabilitiesHTML cannot provideXML different from HTMLXML:not a markup language with defined tagsXML:tags do not specify text appearance on page Cengage Learning 201561 Cengage Learning 201562FIGURE 2-10 Country list data marked up with HTML tags Cengage Le

61、arning 2015 Cengage Learning 201563FIGURE 2-11 Country list data as it appears in a Web browser Cengage Learning 2015Extensible Markup Language(contd.)Advantages of XML list presentationMore effectively communicates the meaning of dataStrength of XMLUsers may define their own tags(weakness as well)C

62、engage Learning 201564 Cengage Learning 201565FIGURE 2-12 Country list data marked up with XML tags Cengage Learning 2015 Cengage Learning 201566FIGURE 2-13 Country list data marked up with XML tags as it would appear in Internet Explorer Cengage Learning 2015Extensible Markup Language(XML)(contd.)S

63、olution to user tag definitionsCommon XML tags standardsData-type definitions(DTDs)or XML schemas2001:W3C released set of rules for XML documentsXML vocabulary:set of XML tag definitionsXML files not intended to display in browserExtensible Stylesheet Language(XSL)contains formatting instructionsXML

64、 parsers:format XML file for device screen Cengage Learning 201567 Cengage Learning 201568FIGURE 2-14 Processing requests for Web pages from an XML database Cengage Learning 2015HTML and XML EditorsHTML document creationGeneral-purpose text editor or word processorSpecial-purpose HTML editors availa

65、bleWeb site design toolsCreate and manage complete Web sitesUpload entire site from PC to Web serverExample:Adobe DreamweaverXML filesCreated with text editor or programsExample:XML Spy Cengage Learning 201569Internet Connection OptionsInternet Set of interconnected networksOrganizations connect com

66、puters using a networkInternet access providers(IAPs)or ISPsProvide Internet access to individuals,businesses,other organizationsOffer several connection options Cengage Learning 201570Connectivity OverviewCommon connection optionsVoice-grade telephone lines,various types of broadband connections,leased lines,wirelessDistinguishing factorBandwidthAmount of data traveling through communication line per unit of timeNet bandwidthActual speed information travelsSymmetric connectionsProvide same band