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CS101 Introduction to Computing Lecture 3 The World Wide Web (Web Development Lecture 1)

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Title: CS101 Introduction to Computing Lecture 3 The World Wide Web (Web Development Lecture 1)


1
CS101 Introduction to ComputingLecture 3The
World Wide Web(Web Development Lecture 1)
2
During the Last Lecture
  1. We learnt about some of the important milestones
    on the journey that started from the Analytical
    Engine and so far has taken us to the portable
    computer-telephone of today
  2. We also saw how computing transitioned from
    mechanical to electro-mechanical to tube to
    transistor technology and now is poised to take a
    breathtaking twist towards quantum computing

3
Todays Goal is to
  • Become familiar with one of the most popular
    activities on computers the World Wide Web
  • Become familiar with the Webs structure and how
    the Web works
  • Learn about its genesis, its evolution, and its
    future
  • About its impact on computing, society, commerce

4
What is the World Wide Web?
  • A huge resource of information
  • Logically unified, but physically distributed
  • Unified Anyone from any where can access the
    information using a very simple scheme consisting
    of hyperlinks URLs
  • Distributed The info is stored on
    Internet-connected computers that are spread all
    over the globe

5
Who is allowed to access the Web?
  • Anyone and every one with a computer and a
    connection to the Internet
  • No nationalistic, ideological, racial, or
    religious restrictions
  • In Pakistan, Web is accessible from any city or
    town that has a phone available

6
The Web is unlike any previous human
inventionBecause it is a world-wide resource,
important to all and shared by all of the people
in the worldEnough about who can access it.
Now let us focus upon how to access itAs some
of you may know, the Web is a collection of Web
pages accessing the Web means accessing one of
those Web pages
7
How do I access/visit a Web page?
  1. Turn your computer on
  2. Connect to the Internet through a modem or
    through your computer network
  3. Launch the browser
  4. Type in the URL of the Web page that you want to
    visit

8
Browser
  • The tool used for accessing the content of the
    Web
  • Browser and the content of the Web have the same
    relationship as the TV has with TV programs
  • 1993 - The 1st major browser Mosaic was
    developed at the National Center for
    Supercomputing Applications (NCSA) at the
    University of Illinois, Urbana-Champaign
  • Initially handled text only, later
    graphics-viewing capability was added
  • Most popular Internet Explorer, Netscape
    Navigator

9
What is a URL?
  • Universal Resource Locator
  • The unique address assigned to each unique page
    on the Web
  • Examples
  • http//dawn.com
  • http//www.vu.edu.pk/altaf
  • http//www.smeda.org.pk

10
Are there any access charges?
  • Most of the info on the Web is available for free
  • There is some for-payment content on the Web,
    which is generally paid with the help of a credit
    card

11
How do I navigate the Web?
  • You go from one Web page to another my clicking
    on a hyperlink
  • Ill explain it to you through the example of my
    own Web page

12
URL
links
13
Hyperlinks
  • The underlined pieces of text in blue are called
    hyperlinks
  • Each hyperlink is a gateway to another Web page
  • All you have to do is click on the hyperlink to
    go to the page corresponding to that hyperlink

14
How many Web pages are there?
  • In 1999 there were 800 million Web pages (15
    trillion (1012) text characters)
  • In the year 2002, the number is estimated to be 8
    billion
  • If you spend a minute reviewing each of these
    pages, it will take more than 15,000 years to go
    through them all

15
Tum salamat raho hazar barasHer baras kay hon
din pachas hazar(140,000 normal years)
16
What is secret behind the explosive 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 the
    Web and they do!
  • DRAWBACKS
  • Inconsistent quality of pages
  • Broken links

17
Some of the popular Web sites?
  • AOL Most popular ISPs Web site
  • Microsoft Most popular software developers Web
    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

18
What is a Web site?
  • A collection of related documents available on
    the Web
  • The first portion of the URLs in the Web pages 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 on a
    single Web site

19
What is a home page?
  • The first, top-most page of a Web site, just like
    the cover of a magazine
  • VUs home page is at http//www.vu.edu.pk

20
What is a Search Engine?
  • They continuously scan the Web and compile a list
    of all the Web pages keywords found on those
    pages
  • The search engine with the largest such list (or
    index) is Google with a list of over 2 billion
    Web pages and over 330 million images
  • We use the search engine by typing a keyword or
    query on its Web page. It looks for those
    keyword in its index, and displays a list of Web
    pages that contain that keyword

21
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24
I know I can read off the Web. Am I allowed to
put my stuff on the Web?
  • Definitely. You just need to have a computer
    that is hooked up to the Internet.
  • You do not require anyones permission to put
    your Web page(s) on the Web
  • Your Web page will be available to all the
    millions of users that have access to the
    Internet the moment you place it on the Web

25
Am I allowed to put my stuff on the Web? (cont.)
  • Next week youll 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

26
Internet ---- Web
?
27
  • 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 other services 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 over those roads. Just like other
    services can use the roads (e.g. wagons), so can
    other services on the Internet (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

28
What info is available on the Web?
  • Information about almost every thing known to
    mankind and then some!
  • The info is in the form of
  • Text
  • Graphics
  • Animation
  • Video
  • Sound

29
  • Impact of the Web on
  • Computing
  • Society
  • Commerce

30
Impact of the Web on Computing(Cost)
  • Every one wants to use the Web
  • That has spurred the demand for computers
  • That, in turn, has reduced the cost of computers,
    software, and Internet access drastically

31
Impact of the Web on Computing(Ease of use)
  • The computers are becoming easier to use because
    the target users are becoming less and less
    sophisticated
  • In the olden times only techies used computers
    now my 4-year old knows things about the machine
    that I never did and probably, never will

32
Impact of the Web on Society
  • User-friendly communication has become much more
    affordable the global village is shrinking
  • Business persons can stay in touch with their
    businesses even without being there for some,
    that has resulted in the destruction of their
    family life

33
Impact of the Web on Commerce
  • Huge impact
  • The moment I take my business to the Web, it
    becomes possible for my customers even those
    that I do not know about - to find out about me
    without me being physically present in their city
  • Suddenly, Im running a global business

34
Who invented the Web Why?
  • Tim Berners Lee British physicist
  • 1989 At the European Center for Nuclear Energy
    Research (CERN) in Geneva
  • He just wanted a way by which scientists could
    easily share documents over computer networks

35
The key weakness of the Web?
  • The Web (as it currently exists) was designed for
    humans to read, not for computers to understand
    and manipulate meaningfully
  • Computers face great problems in dealing with the
    current text- and graphics-based content of the
    Web
  • Here is an example from my own Web page

36
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37
Whats the problem with this page?
  • You (a human) see this page and immediately
    understand what my name is
  • How would a computer know the same fact?
  • For that, the computer needs some help in form of
    a statement
  • NameAltaf Khan
  • OccupationTeaching
  • EmployerVirtual University
  • And so on

38
Precisely for this reason, the Web of the future
will be different from the Web of todayThe Web
of the future will be called the Semantic Web
39
Future of the Web Semantic Web
  • What unique feature distinguishes the Web of
    today with the Semantic Web of tomorrow?
  • Whereas, todays Webs content is designed for
    humans to read the Semantic Webs content will
    be designed for computers to understand
    meaningfully
  • However, the Semantic Web is not a replacement
    but an extension of the present Web, in which
    information is given well defined meaning

40
The Semantic Web
  • Some progress is already being made for adding
    Semantic Content on to the Web, but a lot more
    will happen in the next 5 years
  • To find further info about this exciting
    development read Tim Berners Lee and his
    co-workers paper The Semantic Web that is
    available on the Web as
  • http//www.sciam.com/2001/0501issue/0501berners-le
    e.html

41
Another useful Web page
  • Web page for our Understanding Computers text
    book
  • http//www.hbcollege.com/infosys/parker2000

42
What have we learnt today?
  1. What is the World Wide Web?
  2. How does it work?
  3. About its expected evolution into the Semantic
    Web
  4. The impact of the Web on computing, society, and
    commerce

43
Goal of the Next Lecture
  1. To become familiar with various types of
    computers with respect to their applications and
    scale
  2. To become familiar with the basic components of a
    computer
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