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2_World Wide Web

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					•   Introduction to World Wide Web and its
    working
•   Evolution of World Wide Web
•   Communication Context
•   Future of World Wide Web
•   Fundamentals of World Wide Web
•   Hypertext information and
    communication system using Internet
    Computer network
•   Data Communication operates according
    to a Client / Server Model
•   World Wide Web consists of Pages linked
    to each other using Anchors
•    Require Web browser as client to access
    multiprotocol and hypermedia information
•   World Wide Web supports :
      Ø HTTP  (HyperText Transfer Protocol)
      Ø FTP (File Transfer Protocol)
      Ø NNTP (Network News Transfer Protocol)
              Client




Server                           Client



          Information




         Client         Server
•   1989:Tim Bernes Lee, at CERN, proposed a hypertext system to enable efficient information sharing
•   1990: By the end of 1990 the researchers at CERN had a text mode browser and a graphical Browser for Next computers
•   1991:World Wide Web was released for general usage at CERN
•   1992:CERN began publishing the WWW project
•   1993:Browsers had been developed for many different computer systems
•   1994:WWW became one of the most popular ways to access internet resources




             ♦     1992:CERN began publishing the WWW project
             ♦     1993:Browsers had been developed for many different computer systems
             ♦     1994:WWW became one of the most popular ways to access internet resources
•   Interpersonal : Personal Home Pages offer
    One-to-One Communication
•   Group : Breakdown of Information into
    subject trees such as conferencing or chat
    etc.,
•   Organizational : Information of the
    organization resides on the web
•   Mass : Offers One-to-Many Communications
•   Politics on the Web
•   Using Electronic Education
•   Web Marketing
•   Language is No Barrier
•   Web to Manage Office
•   Taking the Web on the road
•   Web Technical Protocols
•   Browser
•   Web Servers
•   Hypertext
•   Hypertext Markup Language - HTML
•   Links - Hyperlinks
•   Uniform Resource Locator - URL
•   Hypertext Transfer Protocol - HTTP
•   Home Pages
•   Search Engines
•   Common Gateway Interface - CGI
  •It is client program, required to access World Wide Web
  •It formats hypertext documents based on the client
    computer
  •It can access multiprotocol and hypermedia information
  •It can be used to display different media files
  •It can start applications to display documents of a
    particular type
                       Browser request
                       the information
        Client                             Browser

                        Server response


Browser displays the
response
•   Multiple sessions are must
•   Display the latest HTML Tags
•   Browsers should make web navigation easy
•   Browser and E-mail
•   Browser Newsgroup access
•   Software components that provide services
    on the Internet
•   Understand and talk HTTP
•   Receive and Respond HTTP Request with
    Clients
                        Client Http Request
                          Error Response
                       Document send to Client              Server
Client

    Client Process                          Server Process
                               Server receives
     Client Request              the request
      a document
                                                  yes
     Wait for reply              Availability           Accessibility
   Read the header                                No
                               No
  send by the Server                                         Generate header
                                 Send Error
  Open the document            status to client              based on file type
    in the browser
                                                              Send the file and
   based on header
                                                               header to client
•   All documents of World Wide Web are in
    hypertext format
•   It is a text that contains links to other text
•   These documents also contain pictures,
    graphics,sound and animations etc,
•   Documents that contain more than just text
    are called hypermedia
•   Hypertext markup language is a standard for
    writing documents on World Wide Web that could
    be displayed on different kinds of computers
•   It is a set of commands that describe the
    structure of the document to be displayed
•   It is the most commonly used markup language
•   Ease of use and friendliness
•   HTML commands (called tags ) are inserted
    around blocks of text in a documents to describe
    what the text is.
•   HTML can import other media - images, sounds,
    animation etc.,
•   Live References to other documents
•   Links can be to any file type (E.g. web
    pages, sound files, picture files, mail
    addresses, FTP sites, News Groups)
•   Parts of hyperlink:
    Ø URL reference
    Ø Anchor (Graphical/Hypertext)
    Example :
    <A
    HREF=“http://www.yahoo.com/”>Yahoo</A>
ú The Uniform Resource Locator is the common
  format of addressing objects on the World Wide
  Web
ú A Typical URL:


ú http:// servername: port/path/to/file.html




             Indicates that      Specific computer   Path on the
 Protocol
              what follows is    host on which       computer on
 used to
              a valid            the information      which the
 retrieve
                                  resides.           specific resource
 information Internet address.
                                                      resides.
     ¨ Simple English Language Protocol that
       server      and client speak
     ¨ It is a simple request/response protocol
     ¨ HTTP request
              ¡   GET
              ¡   POST
     ¨   HTTP Response
              ¡   HTML
     ¨   It is a stateless protocol

                            Request
                           connection

                           Response
Client/user                                Server
•   It is the main page for a particular Web site
•   The page that is loaded automatically by the
    browser on startup
•   Programs that gather data and present it
    to the Web users in a searchable format.
•   Search Engines provide many valuable
    services
•   Automated search of Web space for new
    sites
•   Indexing of available sites by URL
•   Indexing of sites by page titles, text
    contents, quality of content and ‘freshness’
    of content
•   Some popular search engines are Lycos,
    Yahoo, Excite etc.,
•   CGI lets Web servers to execute external
    programs and incorporate their output
    into a HTML format and send it to a Web
    browser
•   The magic behind web-based interactive
    games, page counters, order entry
    systems, online shipping charts, SQL
    database interfaces, animations and
    clickable images are possible through CGI
•   Written in ‘C’ or ‘PERL’ etc.,
•   CGI scripts can be used for processing
    form, animation, HTML on the fly,
    counters, search engines

				
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posted:10/6/2010
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