The Web q The World Wide Web Web
The Web q. The World Wide Web (Web in short) is the internet application that most people turn to when they want to access or publish information online. q. The Web, in fact, is an architectural framework for accessing linked documents spread over millions of machines all over the Internet. q. It is a large system of Servers (sources of information maintained as series of pages) which offers all kinds of information to any one on the Internet. q. The information can be in the form of regular text, pictures, sound, and other types of data.
Brief History of the Web: � � � In March 1889 Tim Burners –Lee, a programming consultant at the European Center for Nuclear Research (CERN) wrote his proposal for what would become the World Wide Web. Within one year Berners-Lee took the web all the way-from original conception to hacking out primitive browsers and servers, to the creation and elaboration of the protocols needed to make the whole thing work. T he first (text based) prototype was operational 18 months later. In December 1991 a public demonstration was given at the ‘hypertext 91’ conference in San Antomic, Texas. The first browser created by Lee, was also called World Wide Web, the name was later changed to Nexus. Crude as it was, Nexus made real the promise of a global hypertext network. The Web went public on January 15, 1991, and a line- mode browser that was capable only of displaying text was used to view the content. The web grew out of the need to have large teams of internationally dispersed researchers collaborate using a constantly changing collection of reports, blue prints, drawings, photos, and other documents.
History of the Web The first demonstration of the WWW and its attendant publicity caught the attention of other researchers all over the world, efforts started to further simplify its operation. � In January 1993, Marc Anderson unleashed ‘Mosaic’ in the spring of 1993, which made possible to view hypertext documents with embedded graphics, to launch sound files, and to open movie clips and other “reach hypermedia”. � ‘Mosaic’ was the first browser to make it possible for surfers to point and click their way around the Web. Mosaic was so popular that after just one year Anderson formed a company ‘Net-scape Communications Corporation’ to develop clients, servers and other web software. � With the release of ‘Internet Explorer’ by the Mocrosoft Corporation, some kind of a browser war started between the ‘Netscape Navigator’ and ‘Internet Explorer’, each one trying frantically to add new features( and thus more buyers) than the other , contributing further simplification of the Web. �
History of the Web �In 1994, CERN and MIT signed an agreement setting up the World Wide Web consortium, as an organization devoted to further developing the Web, standardizing the protocols, and encouraging interoperatebility between sites. �Berners- Lee became the director of the consortium. Since then, several hundred universities and companies have joined the consortium. �Interested readers are referred there (home page of the consortium-www. w 3. org) for links to pages covering all of the consortium’s numerous documents and activities.
Continued… � The Web is a unique development, combining the wordprocessing abilities, data retrieval-and-storage power, and graphical-display capabilities of the personal computers with the publishing capacity of the Guttenberg’s printing press. Then it throws in all the possibilities of TV, radio, photography, and animation. � The Web demonstrated that the Internet combined the characteristics of all the media that had come before it, while adding the unique, hypertext-driven power of interactivity to the mix. � The key to the Web is that ‘it is a system of organizing, linking, and displaying information in a way that computers allover the world can access, regardless of the operating system they employ, the kind of software they use to render information, the kind of server the information is stored on, or the online network that information is passing through’.
Architectural overview of the Web �From the user’s point of view, the web consists of a vast worldwide collection of documents or Web. Pages. Each page may contain links to other pages any where in the world. Users can follow a link by clicking on it, which then takes them to the page pointed to. This process can be repeated indefinitely. �The idea of having one page point to another, now called hypertext, was invented by a MIT professor of electronic engineering, Vannevar Bush, in 1845.
� � � Web pages called pages in short are viewed with a programme called ‘browser’, for example, the Internet Explorer, and the Netscape Navigator. The browser fetches the page required, interprets the text and formatting commands on it, and then displays the page, properly formatted on the screen. Web pages generally starts with a title, contains some information, and ends with the e-mail address of the pages maintainer, strings of text that are links to other pages , called hyperlinks, are often highlighted, by underlining, displaying them in a special colour, or both. To follow a link , the user places the mouse cursor on the highlighted area, which causes the cursor to change , and clicks on it. Non-graphical browsers, such as Lynx and voice based browsers are also being developed. If the user ever returns to the main page, the links that have already been followed may be shown with a dotted underline (and possibly a different colour) to distinguish them from links that have not been followed.
The web model
How the web function? � � � In shown in the figure, the browser is displaying a web page on the client machine. When the user clicks on a line of text that is linked to a page on abcd. com server, the browser follows the hyperlink by sending a message to the abcd. com server asking it for the page. When the page arrives, it is displayed. If this page contains a hyperlink to a page on the xyz. com server that is clicked on, the browser then sends a request to that machine for the page, and so on indefinitely. To follow a hyperlink and fetch a selected page, the embed hyperlink needs a way to name any other page on the web. Pages are named using URLs (Uniform Resource Locators). A typical URL is http: //www. abcd. com/products. html. To be able to display a new page (or any page), the browser has to understand its format. To allow all browsers to understand all Web. Pages, web pages are written in a standardized language called HTML, which describes web pages.
� � � The Web allows people to retrieve and publish information through use of a single colorful graphical user interface (the Web browser), a simple word processingstyle publishing language (Hypertext Markup of Language, or HTML), and a less simple communication standard (Hypertext Transfer Protocol, or HTTP) that specifies how information on the internet is transmitted and retrieved by controlling how computers issue and respond to requests for information. Any one can create his/her Web information to share with people all over the Net. Within the Web information is stored in pages. Each page can hold not only information but links to other pages. As you read a page, you can follow a link to jump from one page to another. The various pages can be on any computer on the Net. When you want to follow a link, your browser will find out where it is, contact the Web Server at that location, request the new page, and than display it on your computer screen. So what you have to do is just tell your browser the address of something (desired by you) on the Web. When you don’t have the address you can take the help of a Web Search Engine, which can help you search your desired page using the key word you have given. The idea of data containing links to other data is called hypertext. Thus the purpose of the web is to fetch and display pages of hypertext. This simple idea has proved to be so useful and enjoyable , within a short time , that the web has grown to be one of the three most popular internet services, the other two being electronic mail and Usenet discussion groups.
- Slides: 10