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CS101 Introduction to Computing

Lecture 3The World Wide Web

(Web Development Lecture 1)

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During the Last Lecture

We learnt about several importantmilestoneson the modern computings

journey that started with the AnalyticalEngine, and as of today, has brought usto the hand-held computer

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Todays Goal is to

Become familiar with one of the most popular activitieson computers the World Wide Web

We want to become familiar with the Webs structure

About how the Web works

About its genesis, its evolution, and where it is going

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What is the World Wide Web?

A huge resource of information

Logically unified, but physically distributed

Logically unified: Any one from any where can accessthe information using a very simple scheme consistingof links & URLs

Physically distributed: The information is stored onInternet-connected computers that are spread all overthe globe

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Who is allowed to access the Web?

Any one and every one with a computerand a connection to the Internet

No nationalistic, ideological, racial, orreligious restrictions

In Pakistan, Web is accessible from anycity or town that has a phone available

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How do I visit a Web page?

1. Turn your computer on

2. Connect to the internet through a modem orLocal Area Network

3. Launch the browser (which in most cases,

will be the Internet Explorer)

4. Type in the URL of the Web page that youwant to visit

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Browser

Browser is the tool that we use to access the contentof the Web

Browser and the content of the Web have the same

relationship as the TV has with cable programming

1993 - The 1stmajor browser Mosaic was developedat the National Center for Supercomputing

Applications (NCSA) at the University of Illinois,Urbana-Champaign

Initially handled text only, later graphics-viewingcapability was added

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What is a URL?

Uniform Resource Locator

The uniqueaddress assigned to eachunique page on the Web

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Examples

http://dawn.com

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

http://www.smeda.org.pk

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Are there any access charges?

Most of the info on the Web is availablefor free

There is some for-payment content onthe Web, which is generally paid with

the help of a credit card

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Links

The underlined pieces of text in blue are calledlinks

Each link is a gateway to another Web page

All you have to do is click on the link to go tothe page corresponding to that link

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How many Web pages are there?

In 1999 there were 800 million Web pages (15terra (1012) bytes of text)

In year 2002, the number is supposed to be 8billion

If you spend a minute reviewing each of thesepages, it will take more than 15,000 years to go

through them all

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What is secret behind theexplosive growth of the Web?

Anarchy any page is allowed to link to any other

There are no controls over who puts what on the Web

Everyone can put whatever they want to put on theWeb and they do!

DRAWBACKS: Inconsistent quality of pages

Broken links

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The most popular Web sites?

AOLMost popular ISPs Web site

MicrosoftMost popular software developersWeb site

Yahoo Most popular multi-service Web site

Amazon most popular shop on the Web CNN most popular news Web site

Google most useful search engine

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What is a Web site?

A collection of related documents availableon the Web

The first portion of the URLs in the Webpages of a Web site is the same e.g. http://www.vu.edu.pk/

http://www.vu.edu.pk/~altaf http://www.vu.edu.pk/cs101

Are the URLs of three distinct Web pages ona single Web site

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What is a Web Search Engine?

Search engines continuously scan the Web andcompile a list of all the Web pages that they find

The search engine with the largest such list (orindex) is Google with a list of over 2 billionWeb pages and over 330 million images

We use the search engine by typing a searchkey wordor query on its Web page. It looksfor those keyword in its index, and displays a listof Web pages that contain that keyword

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I know I can read off the Web. Am Iallowed to put my stuff on the Web?

Yes. You just need to have a computer that ishooked up to the Internet.

You do not requireanyones permission to putyour Web page(s) on the Web

Your Web page will be available to all themillions of users that have access to the

Internet the moment you place it on the Web

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Am I allowed to put my stuff on the

Web? (cont.) Next weekyoull have the opportunity to do just

that

Youll learn how to develop your own Web page

And how to make it available on the Web

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Internet ---- Web

The Internet and the Web are not the same

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The Internet and the Web are not the same

In fact, the Web is a service that runs over the

Internet. In addition to the Web, there are many otherservices that run over the Internet.

Internet is like the network of roads in a city, whereas

Web is a service like the Bus Service that run overthose roads. Just like other services can use theroads (e.g. wagons), so can other services on theInternet (e.g. ftp). Well have more to say about this

later in the course

However, The following refer to the same thing:

World Wide Web, Web, WWW

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What info is available on the Web?

Information about almost every thingknown to mankind and then some!

The info is in the form of: Text

Graphics Animation

Video

Sound

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Impact of the Web on:

Computing

Society

Commerce

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Impact of the Web on Computing

Every one wants to use the Web

That has spurred the demand for computers

That, in turn, has reduced the cost of computingdrastically

The computers are becoming easier to use because

the target users are becoming less and lesssophisticated

In the olden times only techies used computers; nowmy 4-year old knows things about the machine that I

never did

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Impact of the Web on Commerce

Huge impact

The moment I take my business to theWeb, it becomes possible for mycustomers to find out about me withoutme being physically present in their city

Suddenly, Im running a global business

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The key weakness of the Web?

The Web (as it currently exists) was designedfor human to read, not for computers to

understand and manipulate meaningfully

Computers have a great problem in dealing withthe current text and graphics based Web

Here is an example

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Whats the problem with this page?

You (a human) see this page andimmediately understand what my name is

How would a computer know the same fact?

For that, the computer needs some help

Some help in form of a statement: Name=Altaf Khan

Occupation=Teaching Employer=Virtual University

And so on

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The Future: The Semantic Web

What unique feature distinguishes the Web of today withthe Semantic Web of tomorrow?

Whereas, todays Webs content is designed for humansto read; the Semantic Webs content will be designedfor computers to understand meaningfully

However, the Semantic Web is not a replacement but anextension of the present Web, in which information isgiven well defined meaning

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Another useful Web page

Web page for our Understanding Computers text book

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

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What have we learnt today?

1. What is the World Wide Web?

2. How does it work?

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

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Goal of the Next Lecture

1. To become familiar with various types ofcomputers with respect to their applications and

scale

2. To become familiar with the basic components of acomputer