电子商务chap02中文

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1、Chapter 2电子商务的技术基础电子商务的技术基础Technology Infrastructure:The Internet and the World Wide Web1Learning Objectives学习目标In this chapter,you will learn about:The origin,growth,and current structure of the Internet互联网的起源、发展和现状How packet-switched networks are combined to form the Internet包交换网络构成互联网的原理Internet

2、protocols and Internet addressing互联网协议和地址The history and use of markup languages on the Web,including SGML,HTML,and XMLWWW标注语言的历史和应用，包括SGML,HTML,and XML2Learning Objectives学习目标How HTML tags and links work on the World Wide WebHTML的标记和链接The differences among internets,intranets,and extranets互联网、内部网和外

3、部网的区别Options for connecting to the Internet,including cost and bandwidth factors接入互联网的各种方法以及各自的成本和宽带Internet2 and Semantic Web第二代互联网和语义网3Technology Overview技术展望Computer networks and the Internet form the basic technology structure for electronic commerce.计算机网络以及互联网构成了电子商务的技术基础设施The computers in thes

4、e networks run such software as:在这些网络中，计算机可以运行的软件有：Operating systems,database managers,encryption software,multimedia creation and viewing software,and the graphical user interface操作系统、数据管理、加密软件、多媒体编程和浏览软件、以及图形用户界面4Technology Overview技术展望The Internet includes:互联网包括：The hardware that connects the com

5、puters together and the hardware that connects the networks together网络将计算机彼此连接在一起的技术，再将全球的计算机网络彼此连接形成更大的网络。Rapid change in these technologies requires businesses to be flexible.这些技术的快速变化带来了商业上的柔性化发展。52.3 Packet-Switched Networks 包交换网A local area network(LAN)is a network of computers close together.距

6、离较紧的计算机组成的网络叫做局域网A wide area network(WAN)is a network of computers connected over a great distance.距离较远的计算机组成的网络叫做广域网Circuit switching is used in telephone communication.网络化计算机的早期“线路交换模式”起源于电话通讯。The Internet uses packet switching互联网使用包交换Files are broken down into small pieces(called packets)that are

7、 labeled with their origin,sequence,and destination addresses.在包交换网络中，文件信息被分解成小片断，称作包，这些包上标有表示源地址、次序和目的地地址的电子标签。6Routing Packets路由数据包The computers that decide how best to forward each packet in a packet-switched network are called routers.在包交换网络中，决定每个包的最佳路径的计算机就叫路由器。The programs on these routers use

8、 routing algorithms that call upon their routing tables to determine the best path to send each packet.这个程序把路由算法应用到存储在“路由表”里的信息上，以此来确定优先使用哪个连接的规则。When packets leave a network to travel on the Internet,they are translated into a standard format by the router.局域网和广域网分别使用不同的规则，当包从局域网转到互联网上时就会由“路由器（集线器、

9、交换机和网桥）”自动生成标准包。These routers and the telecommunication lines connecting them are referred to as the Internet backbone.这些路由器和连接他们的电信线路共同构成“互联网主干网”7图2-3 Routing Packets路由结构82.4 Internet Protocols 互联网协议A protocol is a collection of rules for formatting,ordering,and error-checking data sent across a ne

10、twork.协议是一组规则的集合，他规定了网络传输数据的格式和顺序，并检查这些数据中的错误。ARPANET is the earliest packet-switched network.最早的包交换网叫做ARPANETThe open architecture of this experimental network used Network Control Protocol(NCP)which later became the core of the Internet.这种试验性网络的开放式体系结构采用的是网络控制协议，日后就变成了互联网的核心。9Internet Protocols互联网

11、协议This open architecture has four key rules that have contributed to the success of the Internet.这种开放式体系结构实现包括四个关键规则：Independent networks should not require any internal changes to be connected to the network.独立的网络在接入其他网络是不需要进行能和变更Packets that do not arrive at their destinations must be retransmitte

12、d from their source network.没有到达目的地的信息必须从原节点重新传输Router computers act as receive-and-forward devices;they do not retain information about the packets that they handle.路由器计算机不保留处理过的信息包中的信息No global control exists over the network.对网络没有全局控制10Internet Protocols互联网协议The Transmission Control Protocol(TCP)

13、and the Internet Protocol(IP)are the two protocols that support the Internet operation(commonly referred to as TCP/IP).支持互联网基本操作的两个协议是传输控制协议（TCP）和互联网协议（IP）The TCP controls the disassembly of a message into packets before it is transmitted over the Internet and the reassembly of those packets when th

14、ey reach their destination.TCP控制信息在互联网传输前的打包和到达目的地后的重组。The IP specifies the addressing details for each packet being transmitted.IP控制信息包从源地到目的地的传输路径。112.4.2 IP Addresses IP地址IP addresses are based on a 32-bit binary number that allows over 4 billion unique addresses for computers to connect to the I

15、nternet.IPv4 所用的32位（2的32次方）数字可以表示四十多亿个地址。IP addresses appear in dotted decimal notation(four numbers separated by periods).IP数字（地址）一般写成组圆点分隔的数字。They are assigned by three not-for-profit organizations(ARIN,RIPE,and APNIC).IP地址由三家非营利组织负责分配，即美国互联网号码注册中心、欧洲IP注册中心和亚太地区网络信息中心。12IP AddressesIP地址Approximate

16、ly two billion IP addresses are either in use or unavailable for use.由于IP地址区段分配方面的问题，这些IP地址中有大约二十亿个不是被占用就是不可用。Private IP addresses are a series of IP numbers that have been set aside for subnet use and are not permitted on the Internet.私有IP地址是一系列不允许作为数据包在互联网上传输的IP号码，它们是为了子网的使用而特意保留的。IPv6 is a possib

17、le solution that uses a 128-bit hexadecimal number for addresses.运用128位冒号分隔的数字作为地址，IPv6应该是一种可能的解决方法。132.4.3 Domain Names 域名To make the numbering system easier to use,an alternative addressing method that uses words was created.为了便于使用，人们就发明了一种用单词替代数字的地址标记方式。An address,such as ,is called a domain name

18、.类似表示的地址就称为域名。The last part of a domain name(i.e.,.com)is the most general identifier in the name and is called a top-level domain(TLD).域名最右边部分(i.e.,.com)是域名中最通用的部分，也称为顶级域名(TLD)。14表2-1 Top-level Domain Names顶级域名152.4.4 Web Page Delivery网页传输Hypertext Transfer Protocol(HTTP)is the set of rules for del

19、ivering Web pages over the Internet.在互联网上传输页面文件的规则集称为超文本传输协议HTTP uses the client/server model超文本传输协议使用的C/S模式A users Web browser opens an HTTP session and sends a request for a Web page to a remote server.In response,the server creates an HTTP response message that is sent back to the clients Web bro

20、wser.The combination of the protocol name and the domain name is called a uniform resource locator(URL).协议名和域名称为统一资源定位符(URL)。162.4.5 SMTP,POP,MIME,and IMAPE-mail sent across the Internet must also be formatted to a common set of rules,otherwise e-mail created by one company(or Web site)could not be

21、read by a person at another company.通过互联网传输的电子邮件也必须按照一套规则确定格式。否则，由一人所写的电子邮件另一人则无法阅读。Simple Mail Transfer Protocol(SMTP)specifies the exact format of a mail message and describes how mail is to be administered at the Internet and network level.简单邮件传输协议规定了邮件信息的具体格式、电子邮件服务器上邮件的管理方式和互联网上电子邮件的传输方式。172.4.

22、5 SMTP,POP,MIME,and IMAPAn e-mail program running on a users computer can request mail from the companys main e-mail computer using the Post Office Protocol(POP).在用户计算机上运行的电子邮件客户机程序可以向邮局协议（POP）的电子邮件服务器请求查阅电子邮件。Multipurpose Internet Mail Extensions(MIME)allow the user to attach binary files to e-mail

23、.多用互联网邮件扩展(MIME)The Interactive Mail Access Protocol(IMAP)performs the same basic functions as POP,but includes additional features.交互式邮件访问协议(IMAP)182.5 Markup Languages and the Web标注语言和网页Web pages are marked with tags to indicate the display and formatting of page elements.网页标注语言规定了插入文本中的标记。SGML is

24、 a meta language,which is a language that can be used to define other languages.SGML是一种元语言，它可以用来定义其他标注语言。HTML and XML are both derivatives of SGML.HTML and XML是SGML的两个衍生物。192.5.1 Standard Generalized Markup Language标准通用标注语言SGML offers a system of marking up documents that is independent of any softw

25、are application.SGML提供了一套标注文档的系统，该系统独立于其他任何应用软件。Advantages of SGML include its long-term viability,it is nonproprietary and platform-independent,and it supports user-defined tags and architectures.SGML的优点包括没有专利限制、与平台无关、允许用户自定义标记。Disadvantages of SGML include a costly and complicated set up,expensive

26、 tools,creating document-type definitions that are time consuming,and extensive learning time.SGML的缺点包括不能快速生成页面、建立和维护SGML的成本很高、需要使用昂贵的软件工具、而且难于学习。20Hypertext Markup Language超文本标注语言HTML is a simplified subset of SGML that includes tags defining the format and style of text elements in a document.HTML

27、是更早也更复杂的文本标注语言SGML的子集HTML is an instance of one particular SGML document type.HTML较之SGML更易于学习和使用。HTML now includes tags for tables,frames,and other features that help Web designers create more complex page layouts.HTML的新版本支持表格、页框和其他标记，能帮助页面设计者创建复杂的页面。21Extensible Markup Language扩展标注语言Unlike HTML,XML

28、 uses markup tags to describe the meaning of the text rather than its display characteristics.与HTML不同的是，XML使用的标记是用来描述文字的含义，而不是定义它的特征。XML uses paired start and stop tags in much the same way as database software defines a record structure.XML使用成对的开头和结尾标记，类似于在数据库系统中定义以一条记录。An XML document can be embed

29、ded within an HTML document.XML文档要嵌入在HTML中。XML allows a user to extend the language by creating their own tags.XML允许用户扩展语言来创建它们自己的标记。22图2-4 Markup Languages and the Web231、HTML Tags HTML标记An HTML document contains both document text and elements.HTML文档包含文档文本和元素Tags are codes that are used to define

30、where an HTML element starts and(if necessary)where it ends.In an HTML document,each tag is enclosed in brackets().在HTML文档中，标记放在尖括号()中。A two-sided tag set has an opening tag and a closing tag.大部分HTML 标记都有开始标记和结束标记。242、HTML Links HTML的链接Hyperlinks are bits of text that connect the current document to

31、:超连接是连接当前文档的文字表示符号。another location in the same document在同一个文档中的其他位置another document on the same host machine在同一个主机的不同文档another document on the Internet在互联网络中的不同文档Hyperlinks are created using the HTML anchor tag.超连接是用HTML定位标记创建的Two popular link structures are:两种普通的超连接Linear hyperlink structure线性超连接结

32、构Hierarchical hyperlink structure分层超连接结构25Scripting Language and Style Sheet Capabilities3、脚本语言和风格表单Web designers can use the OBJECT tag to embed scripting language codes in HTML pages(this is also called client-side scripting).网页设计者能用对象标记将脚本语言代码嵌入到HTML页面中。Scripts can execute programs on computers t

33、hat display those pages.脚本嵌入到页面后，会在显示该页面的计算机上执行程序Cascading Style Sheets(CSS)let designers define formatting styles that can be reapplied to multiple Web pages.层叠式风格表单允许设计者定义用于多个页面的各式风格26HTML Editors网页编辑器HTML documents can be created in any general-purpose text editor or word processor.网站设计者可以用普通的文本编

34、辑软件或字处理软件来创建HTML文档Sophisticated editors can create full-scale,commercial-grade Web sites with database access,graphics,fill-in forms,and display the Web page along with the HTML code.高级的网站设计者可以创建各种访问数据库、具备图形和填表功能的商业及网站。（所见即所得）Microsoft FrontPage and Macromedia Dreamweaver are examples of Web site bu

35、ilders.常见的网站设计软件由Microsoft FrontPage 和 Macromedia Dreamweaver 27HTML Editors网页编辑器28Intranets and Extranets内部网和外部网Intranets内部网An intranet is an interconnected network(or internet small“i”intended)that does not extend beyond the organization that created it.内部网是组织内部使用TCP/IP协议的互联网络Intranets are an extr

36、emely popular and low-cost way to distribute corporate information.内部网是传播企业信息的一种流行方法，而且成本也很低。An intranet uses Web browsers and Internet-based protocols(including TCP/IP,FTP,Telnet,HTML,and HTTP)and often includes a firewall.内部网使用基于互联网的协议和常用的防火墙。29Intranets and Extranets内部网和外部网Extranets外部网Extranets a

37、re intranets that have been extended to include specific entities outside the boundaries of the organization(business partners,suppliers,etc.).外部网时间公司与供应商、业务伙伴和其他授权用户连接起来的网络An extranet can be a public network,a secure(private)network,or a virtual private network(VPN).外部网可以是一个公共网络，可以是以专用网络，也可以是一个虚拟专用

38、网(VPN)。302.6 Intranets and Extranets内部网和外部网A public network is any computer or telecommunications network that is available to the public.公共网络是公众可用的任何计算机网络或电信网络。A private network is a private,leased-line connection between two companies that physically connects their intranets to one another.专用网络是两个

39、企业间的专线连接，这种连接是两个企业的内部网之间的物理连接。A VPN extranet is a network that uses public networks and their protocols to send sensitive data to partners,customers,suppliers,and employees using a system called IP tunneling or encapsulation.虚拟专用网的外部网是一种特殊的网络，它采用一种叫做“IP通道”或“数据封装”的系统，用公共网络及协议向贸易伙伴、顾客、供应商和雇员发送敏感的数据。31

40、2.7 Internet Connection Options互联网接入方案The Internet is a set of interconnected networks.互联网有一系列相互连接的网络组成。Large firms that provide Internet access to other businesses are called Internet Access Providers(IAPs)or Internet Service Providers(ISPs).为其他企业提供接入服务的企业叫互联网接入服务商(IAPs)或叫网络服务供应商。322.7.1 Connectivi

41、ty Overview接入概述The most common connection options that ISPs offer to the Internet are telephone,broadband,leased-line,and wireless.ISP为顾客提供多种互联网接入方式。最常见的接入方式有：电话、宽带、专线和无线。Bandwidth can differ for data traveling to or from the ISP.不同的ISP所提供的连接带宽是不同的。Bandwidth is the amount of data that can travel thr

42、ough a communication line per unit of time.带宽是单位时间内通过一条通信线路的数据量。332.7.2 Voice-Grade Telephone Connections语音级电话接入The most common way to connect to an ISP is through a modem connected to your local telephone service provider.与ISP建立连接的常用方法是通过调制解调器连接本地电话服务商。POTS uses existing telephone lines and an anal

43、og modem to provide a bandwidth of 28-56 Kbps.传统电话服务使用现有的电话线和模拟调制解调器可提供28-56 Kbps的带宽。ISDN uses the DSL protocol suite to offer bandwidths between 128-256 Kbps.综合业务数据网是最早应用DSL协议的使用技术，它可以提供128-256Kbps的带宽。342.7.3 Broadband Connections宽带接入Connections that operate at speeds of greater than 200 Kbps are c

44、alled broadband services.超过200 Kbps 的接入称为宽带服务。ADSL uses the DSL protocol to provide bandwidths between 100-640 Kbps upstream and 1.5-9 Mbps downstream.非对称数字用户线路ADSL使用DSL协议提供宽带服务，可提供100-640 Kbps 的上行带宽和1.5-9 Mbps 的下行带宽。Cable modems provide transmission speeds between 300 Kbps-1 Mbps from the client to

45、 the server and a downstream rate as high as 10 Mbps.连接有线电视同轴电缆的线缆调制解调器提供300 Kbps-1 Mbps 的上行带宽和10 Mbps 的下行带宽Satellite microwave transmissions handle Internet downloads at speeds around 500 Kbps.卫星微波传输提供下行的带宽为500 Kbps352.7.4 Leased-Line Connections专线接入Large firms can connect to an ISP using higher-ba

46、ndwidth connections that they can lease from telecommunications carriers.大公司与ISP建立连接时，可以从电信公司那里租用更高的带宽。A T1 line operates at 1.544 Mbps and a T3 line operates at 44.736 Mbps.一条T1线路，带宽1.544 Mbps，一条T3线路，带宽44.736 Mbps。362.7.5 Wireless Connections无线接入Many researchers and business managers see great pote

47、ntial for wireless networks and the devices connected to them.许多研究机构和商业管理看到了无线网络和连接它们的设施的巨大潜力The term m-commerce(mobile commerce)is used to describe the kinds of resources people might want to access using devices that have wireless connections.移动贸易通常是用来描述人们利用无线连接设备来接近各种各样的资源。37表2-2 Internet Options

48、 互联网的接入方案382.8 Internet2 第二代互联网Internet2 is an experimental test bed for new networking technologies that is separate from the original Internet.第二代互联网实行网络技术的试验平台200 universities and a number of corporations joined together to create this network.200所大学和许多企业加入到一起构成了这个网络。It has achieved bandwidths of

49、 10 Gbps.它的带宽能达到10Gbps以上。Internet2 promises to be the proving ground for new technologies and applications of those technologies that will eventually find their way to the Internet.第二代互联网主要专注于技术开发。39复习题1.导致互联网商业化的主要原因是什么？2.用一两段话描述一下HTML的起源，要介绍一下标记，并介绍在HTML发展中起重要作用的几个人；3.比较POP电子邮件协议和IMAP电子邮件协议的异同，分别适

50、合什么环境？为什么？（200字以内）4.描述XML与HTML之间的异同，对每一种语言各举两个应用例子？（400字以内）5.网络的接入方式有哪些？其优缺点又如何？对每种方法至少列举两种优点和两种缺点。401、What were the main forces that led to the commercialization of the Internet?Summarize your answer in about 100 words.The Internet was born out of the need for the U.S.government,specifically the De

51、fense Department,to communicate with its weapons installation distributions all over the world.This idea,in the hands of researchers and scientists evolved even further allowing those researchers the capability to communicate with their colleagues at other universities.As personal computers became m

52、ore popular and affordable,companies increasingly wanted to construct their own networks.This all led to the dramatic increase in business activity,but the commercialization of the Internet was really spurred by the emergence of the World Wide Web.The software that allowed computers to communicate w

53、hile on the Internet is still the largest category of traffic today.412、Describe in one or two paragraphs the origins of HTML.Explain how markup tags work in HTML,and describe the role of at least one person involved with HTMLs development.SGML is a software language for describing electronic docume

54、nts and how they should be formatted as well as displayed.This language is the precursor of HTML,which is used by all documents on the Web.Robert Calliau and Tim Berners-Lee independently invented HTML at the CERN research center in Switzerland.HTMLs document type definition is easier for users to l

55、earn and use for describing formatting and displaying electronic documents by Meta tag codes.423、In about 200 words,compare the POP e-mail protocol to the IMAP e-mail protocol.Describe situations in which you would prefer to use one protocol or the other and explain the reasons for your preference.A

56、 POP message can tell the e-mail computer to send mail to the users computer and to delete it from the e-mail computer;to send mail to the users computer and do not delete it;or simply to ask whether new mail has arrived.IMAP protocol that performs the same basic functions as POP,but includes additi

57、onal features that can instruct the e-mail server to send only selected messages to the client instead of all messages.It also allows the user to view only the headers and the e-mail senders name before deciding to download the entire message.One would choose IMAP if they have a need for a more robu

58、st system that allows them to access their email from different computers at different times.434、In about 400 words,describe the similarities and differences between XML and HTML.Provide examples of at least two situations in which you would use XML and two situations in which you would use HTML.XML

59、 and HTML are similar in that they are both powerful tools for creating web pages that use tags to organize data.However,XML is not a markup language with defined tags,as is HTML.XML is a framework within which individuals,companies and others can create their own tags.These tags do not specify how

60、the text will appear on a web page the tags convey the meaning of the information included with them.One would choose HTML if they were building a simpler page that did not require data management capabilities.HTML also allows the developer to embed scripting language code giving them more control o

61、ver the format of displayed pages.XML is very useful for sites that have lists that require updating such as inventory items,purchase orders,etc.XML is far superior to HTML for data management.XML also allows developers to create a tag for each fact that define the meaning of the fact.445、Use your f

62、avorite search engine and the links in the Online Companion(under the heading“Internet Connection Options”)to search for more information about broadband satellite connections,DSL connections,wireless connections and cable connections.Prepare a four-column table(one column for each technology)in whi

63、ch you list the advantages and disadvantages of each connection method.45Answers will vary but should include the following:SatelliteDSLWirelessCableAdvantagesUpstream transmission-100 640 Kbps150 Kbps300 Kbps-MbpsDownstream transmission500 Kbps1.5 9 Mbps500 KbpsUp to 10 MbpsDisadvantagesSatellite users have to rely on plain old telephone system to upload filesInstallation can be quirkyUnusable for people living in large citiesConnection bandwidth varies with the number of subscribers46