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CSCI1412 Lecture 4

phones off (please). CSCI1412 Lecture 4. The Internet 1 Communicating with Others Dr John Cowell. Overview. The Internet history and organisation The world wide web web pages (HTTP and HTML) browsing the internet Web authoring design issues, authoring tools Other Internet features

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CSCI1412 Lecture 4

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  1. phones off(please) CSCI1412Lecture 4 The Internet 1Communicating with Others Dr John Cowell CSCI1412-I-1

  2. Overview • The Internet • history and organisation • The world wide web • web pages (HTTP and HTML) • browsing the internet • Web authoring • design issues, authoring tools • Other Internet features • search engines • email, ftp • future of the Internet? CSCI1412-I-1

  3. The Internet CSCI1412-I-1

  4. The Development of the Internet • Started as US Department of Defence network • Advanced Research Projects Agency (ARPAnet), • distribute US military computing capability • resist (nuclear) attacks / natural disasters • A 4 node Arpanet working - November 1969 • First network email – 1971 • First Arpanet connection outside the US (to Norway) 1973 • First File Transfer (FTP) – 1973 • All links converted to TCP/IP 1983 • Administered by the US government until 1992

  5. Internet Penetration

  6. World Internet Usage

  7. Internet Languages

  8. Internet Administration • The Internet Society (ISOC) • Nonprofit organisation founded in 1992 to provide leadership in Internet related standards, education, and policy. • A global clearing house for Internet information and education • Coordinator of Internet-related initiatives around the world. • Includes: • Internet Engineering Task Force (IETF) governs administrative and technical activities. Adopts some Requests for Comments (RFCs) as Internet Standards • The Internet Architecture Board (IAB). technical activities of the Internet including writing spec’s and protocols . • Full details at - http://www.isoc.org CSCI1412-I-1

  9. Internet Domains • Internet sites need two pieces of information • domain name from domain name service (DNS) • registered by Internet Corporation for Assigned Names and Numbers InterNIC • IP address, such as 123.123.123.123 • Domains are hierarchical • top/primary level - WWW.DMU.AC.UK • secondary level - WWW.CSE.DMU.AC.UK • Political, commercial and organisational domains • .GOV, .COM, .ORG, .BIZ, .TV • ISO country names • .UK, .NL, .AU • Domains within countries • .AC, .CO CSCI1412-I-1

  10. The World Wide Web CSCI1412-I-1

  11. The World Wide Web • A part of the Internet • open information sharing • interconnected pages of information • ‘Governed’ by WWW Consortium (W3C.ORG) • Pages/sites are interconnected by hypertext links • non-linear documents • first proposed by Ted Nelson in 1963 • links point to other documents • selecting the link • requests web-page and/or moves to that point within current document CSCI1412-I-1

  12. WWW Browsers • Browsers are not all the same • different versions • different sets of commands • Different things happen if the XHTML is invalid • Mosaic • written by students at University of Illinois • Marc Andreesen and Jim Clark founded Netscape • Netscape 7.0 • Mozilla - Firefox 2.0 • Microsoft’s Internet Explorer 7 • Opera 9 CSCI1412-I-1

  13. How the Web Works • User types uniform resource locator (URL) • maps to IP address using DNS • Browsers use hypertext transfer protocol (HTTP) • HTTP requests document from host system • returns document • or error message • not found (404) • no permission to access (403) • Browser reads tags in document • tags control layout of document objects • link tags are used to request further objects • e.g. graphic, sound, video files CSCI1412-I-1

  14. Hypertext • Hypertext mark-up language (HTML) • uses tags to control layout of objects on web-page • Replaced in 2000 by XHTML. Similar in appearance to HTML • Tags appear between angled brackets • <br /> • Most tags work in pairs • <html></html> • <a></a> • View the source code of any web-page • unless facility has been disabled • Netscape: View|Page Source • Explorer: View|Source CSCI1412-I-1

  15. Example XHTML <?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Home page</title> <link href="style.css" type="text/css" rel="stylesheet" /> </head> <body> <p> This is my home page </p> </body> </html> CSCI1412-I-1

  16. Web Authoring CSCI1412-I-1

  17. Web-Site Design • Site design must be fluid • adopt a prototyping design approach • if building a site for a client • get them involved • listen to their ideas • display your work regularly • Four considerations • aims • target audience • purpose • content • These issues may change as web-site develops CSCI1412-I-1

  18. Aims and Target Audience • Aims • what goals do you intend your web-site to achieve? • your hobbies, interests? • commercial sites • new products details • easy ordering • Target audience • who do you expect to visit your site? • general groups • what are their motivations? • what will be their expectations? CSCI1412-I-1

  19. Purpose and Content • Purpose • what is the reason for building the web-site? • what should your visitors be able to achieve? • purchasing • contact • complaints • Content • what is the page content / layout? • use storyboarding for initial design • cascading style sheets? • frames? • where do text / graphics come from? CSCI1412-I-1

  20. Authoring Tools • HTML editors • Notepad • Products such as "Enhanced HTML" • allows direct entry of HTML tags • wizards may do the more complex bits • WYSIWYG authoring package • Netscape Composer • FrontPage • DreamWeaver • Flash, Director • On-line authoring; for example: • www.Angelfire.com CSCI1412-I-1

  21. Web-Site Maintenance • Keep site up to date • there is nothing worse than visiting a web-site that hasn’t been touched for two years • and is now totally out of date! • Add a ‘last updated’ text object to page • Check to see that all links (on- and off-site) are still active • ask your visitors to let you know of any broken links CSCI1412-I-1

  22. Other Internet Features CSCI1412-I-1

  23. Search Engines • Search engines use their own database of entries • web authors upload key words/phrases • Single • UK • Excite, Lycos • world wide • Yahoo, AltaVista,Google • Multiple • AskJeeves • Copernic- searches within results, stores web pages, customisedhttp://www.copernic.com/en/products/agent/index.html CSCI1412-I-1

  24. Other Internet Facilities • WWW is just one part of the internet • many other top layer protocols/features • email, FTP, • telnet • Allows one computer to connect to another and act as a terminal of that computer. Superseded by remote login. • archie • Developed at the Computer Science Department at McGill University in Montreal, - a public domain tool for finding files on anonymous ftp sites. The Archie database currently indexes more than 2,100,000 files contained in more than 1000 anonymous ftp sites around the world. See http://www.acad.bg/beginner/gnrt/specialist/archie.html • ping • signal sent out by one server to another, asking for a response, checks latency and presence of servers • traceroute • tracks & displays route packets take between client and host CSCI1412-I-1

  25. email • Simple Mail Transfer Protocol (SMTP) • all outgoing email sent by this protocol • POP3 / IMAP • mail receiving systems • Post Office Protocol • mail is stored, copied to PC when on-line, read off-line • Eudora, Outlook Express, Pegasus Mail, Netscape Messenger • interactive Mail Access Protocol • log on to remote server, read mail on-line • Yahoo, Hotmail CSCI1412-I-1

  26. email Features • Address books • typing first few characters of an address will access the relevant record in the address book • Contact groups • list of email addresses • mail the contact list name - mail goes to all members of list • Attachments • single or multiple documents attached to email • get a ‘piggyback’ ride to recipient(s) CSCI1412-I-1

  27. FTP • File Transfer Protocol • allows easy transfer of files between remote systems • whole directory trees in single transaction • other file maintenance facilities • directory / folder management • create, change, remove, etc • file management • delete, move, copy, etc. • superior error recovery than browser downloads • DMU FTP server is ftp.cms.dmu.ac.uk • Instructions page • http://www.cse.dmu.ac.uk/~cfi/Reference/UseFTP.htm CSCI1412-I-1

  28. CORE-FTP • Shareware - drag & drop CSCI1412-I-1

  29. Future of the Internet? • Multimedia, speeds need to be increased • Increasingly used for social activities, YouTube, Facebook • Virtual living – Second Life • Virtual Reality ModellingLanguage (VRML) • three-dimensional graphics on web pages • http://www.ocnus.com/vrml.html • Stargazing web-site • http://internetbrothers.com/futureshock.htm CSCI1412-I-1

  30. Summary • The Internet • history and organisation • The world wide web • web pages (HTTP and HTML) • browsing the internet • Web authoring • design issues, authoring tools • Other Internet features • search engines • http://searchenginewatch.com/webmasters/article.php/2168031 • email, ftp • future of the Internet? CSCI1412-I-1

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