Transcript Introduction to the World Wide Web

Introduction to the
World Wide Web
Lecture 1
Introduction
The WWW Environment
Welcome!
Learning aims
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An understanding of the WWW environment and
how it works.
An introductory understanding of the principles and
process of website design, including the human
computer interface elements, usability, and
standards compliance.
An overview of eCommerce and online business
information systems, web security and ethics, and
future possibilities in web technology and
applications.
The ability to apply concepts in (2) above to critique
websites.
Aims continued…
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A broad understanding of graphics, colours, sound
and video for the web, and the ability to select
suitable content in the appropriate format.
The practical skills and knowledge to implement
concepts in (2) and (3) above in constructing a
simple website using a WYSIWYG web authoring
tool, emphasising design appropriateness,
standards compliance and accessibility, and
incorporating cascading style sheets and JavaScript.
In this lecture…
The World Wide Web environment
 Describe the history and development of the
WWW
 Describe WWW content
 Computer Network, protocols
 URL address
What is the WWW?
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Worldwide collection of documents
Shelly, Cahsman, Vermaat: Discovering Computers 2007
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Multimedia-based collection of information, services
and Web sites supported by the Internet
Haag, Cummings, Rea: Computing Concepts
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Part of the Internet, a collection of multimedia
documents…linked in a hypertext Web that allows
users to explore them with simple mouse clicks
Beekman & Quinn: Computer Confluence
Key elements
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The WWW is made available over the
Internet
A collection of resources - text, graphics,
video, sound
There is interaction - e.g. through hyperlinks
It is multi platform - should work with any
computer/PDA/phone
It is decentralised - it is a web
WWW History
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Developed in 1989/1990 by Tim Berners-Lee, at
CERN, a physics research facility in Switzerland
He developed the…
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Addressing system (URL)
Web page language (HyperText Markup Language, HTML)
The linking protocol (HyperText Transfer Protocol, HTTP)
“The dream behind the Web is of a common information space
in which we communicate by sharing information. Its
universality is essential: the fact that a hypertext link can point
to anything, be it personal, local or global, be it draft or highly
polished.”
Tim Berners-Lee
http://www.w3.org/People/Berners-Lee/ShortHistory
Academic to public
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Use of the web passed from mostly government and
academic use to the general public, assisted by two
developments
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Graphical web browsers in 1994
Commercial use of the WWW permitted from 1995
The development of the cheaper, more user friendly
PC/Mac through the 1990s
From here, the WWW exploded
In a sense, the man who invented it gave it away,
free for everyone to use
What is on the WWW?
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Brochure websites
Interactive websites
Blogging and social networking
Forums
Search engines
On-line business applications
Services such as web-based email, instant
messaging
And more…new things all the time
Brochure sites
Interactive sites
http://scienceview.berkeley.edu/showcase/
Blogging
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A blog (short for web log) is a website where entries
are made and displayed in a reverse chronological
order.
Blogs provide commentary or news on a particular
subject, such as food, politics, or local news; some
function as more personal online diaries.
A typical blog combines text, images, and links to
other blogs, web pages, and other media related to
its topic.
The ability for readers to leave comments in an
interactive format is an important part of most blogs.
Examples of blogs
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Engadget http://www.engadget.com/
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Jonathan’s blog http://blogs.sun.com/jonathan/
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Collaborative blog on new technology
The CEO of Sun Microsystems
A mix of good blogs is at
http://blogs.guardian.co.uk/index.html
Forums
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An Internet forum is a facility on the World
Wide Web for holding discussions and
posting user generated content, or the web
application software used to provide this
facility.
Internet forums are also commonly referred
to as web forums, message boards,
discussion boards, discussion groups,
discussion forums, bulletin boards, fora or
simply forums.
http://www.carforums.com/forums
/
http://forums.pcworld.com/forums
/
Search Engines
Google is very good…try Vivisimo, a
clustering search engine
On-line business applications
The Internet as a Network
A computer network
“A communications system connecting two or more
computers that work together to exchange information and
share resources”
May be…
 Home network
 Office network
 Campus network
 City-wide network
 World-wide
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The Internet “The network of networks”
What is the difference
between WWW and Internet?
Key words
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Node
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Client
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Any device connected to a network
Your computer at home, one in the lab, one out there on the
internet
Has a unique network address
Any node that requests and uses resources available from other
nodes.
Usually from another computer, often a computer called a server
Server
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A node that shares resources with other nodes
File server, print server, mail server or web server
Client-server relationship
Suggested reading - Chapter 2, Discovering Computers 2007
Packet switched vs. circuit switching
networks
Packets (units of information) are routed between
nodes over data links shared with other traffic
 Contrasts with circuit switching, which sets up a
dedicated connection between the two nodes for
their exclusive use for the duration of the
communication like telephone call connection.
Packet switching advantages…
 Makes best use of the capacity in a network
 Improves time it takes for data to pass across the
network
 Increases the stability of the network
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Packet switching
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Files to be transmitted are divided into packets
Labelled with to, from, and # of #
Sent across the network…may take different routes
Put together at the destination
Missing packets are re-sent
Protocols
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The standards that specify how the network
functions
The set of rules for communication over the
network
The language or the grammar that allows
computers to “talk” to each other
The Internet uses many protocols
Internet protocol suite
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Designed to be independent of the underlying
physical medium
Any communications network, wired or
wireless, that can carry two-way digital data
can carry Internet traffic
Thus, Internet packets flow through wired
networks like copper wire, coaxial cable, and
fibre optic, and through wireless networks like
Wi-Fi. Together, all these networks, sharing
the same protocols, form the Internet
TCP/IP
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IP - Internet Protocol
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Handles the packets
TCP - Transmission Control Protocol
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Handles the sending (routing) of the packets from
sender to receiver via nodes on the network
FTP
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File Transfer Protocol
Used to transfer data from one computer to
another over the Internet, or through a
network
Example - create a website on your machine;
use FTP to copy the site to the web server;
now everyone can use the site
Then use FTP to update the files as you
maintain the site
Internet addresses
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IP address
Unique to each device connected
4 groups of numbers, each separated by a
full-stop.
Each of the four numbers is 0 - 255
A word equivalent (URL - uniform resource
locator) is easier to remember
216.239.39.99 = www.google.com
Using URLs
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Complete URLs - Includes the protocol, domain name,
path, and file name. Refers to another server on the
Internet.
Partial URLs - Omits the protocol and domain name.
Refers to a file that resides on the same server.
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If you have time, show the movie Warriors of
the Net
12 minutes long
File is warriors of the net.mpg, in the
lectures folder