World Wide Web, Web’s structure, genesis, its evolution

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Introduction to Computing CS101

LESSON 3

Today's Goal is to ...

Become familiar with the World Wide Web

Become familiar with the Web's structure and how the Web works

Learn about its genesis, its evolution, and its future

About its impact on computing, society, commerce

3.1

Browser

A browser is an application program that provides a way to look at and interact with all the information

on the World Wide Web. The word "browser" seems to have originated prior to the Web as a generic

term for user interfaces that let you browse (navigate through and read) text files online. By the time the

first Web browser with a graphical user interface was generally available (Mosaic, in 1993), the term

seemed to apply to Web content, too. Technically, a Web browser is a client program that uses the

Hypertext Transfer Protocol (HTTP) to make requests of Web servers throughout the Internet on behalf

of the browser user.

3.2 URL

URL (Uniform Resource Locator, previously Universal Resource Locator) - pronounced YU-AHR-EHL

or, in some quarters, UHRL - is the address of a file (resource) accessible on the Internet. The type of

file or resource depends on the Internet application protocol. Using the World Wide Web's protocol, the

Hypertext Transfer Protocol (HTTP), the resource can be an HTML page (like the one you're reading),

an image file, or any other file supported by HTTP. The URL contains the name of the protocol required

to access the resource, a domain name that identifies a specific computer on the Internet, and a

pathname (hierarchical description of a file location) on the computer.

On the Web (which uses the Hypertext Transfer Protocol), an example of a URL is:

http://www.ietf.org/rfc/rfc2396.txt

Which describes a Web page to be accessed with an HTTP (Web browser) application that is located on

a computer named www.ietf.org. The pathname for the specific file in that computer is /rfc/rfc2396.txt.

An HTTP URL can be for any Web page, not just a home page, or any individual file.

Examples:

http://dawn.com

http://www.vu.edu.pk

http://www.smeda.org.pk

3.3 What is a Web site?

A Web site is a related collection of World Wide Web (WWW) files that includes a beginning file

called a home page. A company or an individual tells you how to get to their Web site by giving you the

address of their home page. From the home page, you can get to all the other pages on their site. For

example, the Web site for IBM has the home page address of http://www.ibm.com. IBM's home page

address leads to thousands of pages but a web site can also be just of few pages.

http://www.vu.edu.pk/

Introduction to Computing CS101

3.4 What is Home Page of a web site?

1) For a Web user, the home page is the first Web page that is displayed after starting a Web browser

like Netscape's Navigator or Microsoft's Internet Explorer. The browser is usually preset so that the

home page is the first page of the browser manufacturer. However, you can set it to open to any Web

site. For example, you can specify that "http://www.yahoo.com" or "http://whatis.com" be your home

page. You can also specify that there be no home page (a blank space will be displayed) in which case

you choose the first page from your bookmark list or enter a Web address.

2) For a Web site developer, a home page is the first page presented when a user selects a site or

presence on the World Wide Web. The usual address for a Web site is the home page address, although

you can enter the address (Uniform Resource Locator) of any page and have that page sent to you.

3.5 Who invented the Web & Why?

"CERN is a meeting place for physicists from all over the world, who collaborate on complex physics,

engineering and information handling projects. Thus, the need for the WWW system arose "from the

geographical dispersion of large collaborations, and the fast turnover of fellows, students, and visiting

scientists," who had to get "up to speed on projects and leave a lasting contribution before leaving."

CERN possessed both the financial and computing resources necessary to start the project. In the

original proposal, Berners-Lee outlined two phases of the project:

First, CERN would "make use of existing software and hardware as well as implementing simple

browsers for the user's workstations, based on an analysis of the requirements for information access

needs by experiments."

Second, they would "extend the application area by also allowing the users to add new material."

Introduction to Computing CS101

Berners-Lee expected each phase to take three months "with the full manpower complement": he was

asking for four software engineers and a programmer. The proposal talked about "a simple scheme to

incorporate several different servers of machine-stored information already available at CERN."

Set off in 1989, the WWW quickly gained great popularity among Internet users. For instance, at 11:22

am of April 12, 1995, the WWW server at the SEAS of the University of Pennsylvania "responded to

128 requests in one minute. Between 10:00 and 11:00

3.6 Future of the Web: Semantic Web

The Semantic Web is an idea of World Wide Web inventor Tim Berners-Lee that the Web as a whole

can be made more intelligent and perhaps even intuitive about how to serve a user's needs. Berners-Lee

observes that although search engines index much of the Web's content, they have little ability to select

the pages that a user really wants or needs. He foresees a number of ways in which developers and

authors, singly or in collaborations, can use self-descriptions and other techniques so that context-

understanding programs can selectively find what users want.

3.7 Useful Web page

Web page for our "Understanding Computers" text book

http://www.hbcollege.com/infosys/parker2000

What have we learnt today?

What is the World Wide Web?

How does it work?

About its expected evolution into the Semantic Web

The impact of the Web on computing, society, and commerce

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