CSE3325: Behind
the (World Wide) Web
In the previous lecture:
- A medium is something through which a message can pass.
- Working with multiple media requires an understanding of:
- the different media
- the way the media work together
- the relationship between the media and the message
In this lecture:
- What is the World Wide Web (WWW)?
- How does the WWW simplify Internet information retrieval?
What is the World Wide Web?
- A stage in the history of attempts to make the Internet accessible.
- A collection of hyper-linked documents containing text, sound, graphics
(multiple media!) stored in many different file formats.
- An example of computer-based, interactive multimedia
What is the Internet?
- Began as a de-centralized system of US defence force computers (late 70's)
- Government agencies, scientific research labs, universities etc. started
connecting their computers to the network (the 80's).
- Eventually spanned substantial portion of the developed world (the 90's).
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What is TCP/IP (Transmission
Control Protocol/Internet Protocol)?
TCP/IP is a low-level protocol by which Internet computers of different
makes, models and operating systems communicate.
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Why be connected to the Internet?
The optimist: You want to share information or you find it interesting!
The cynic: You think its trendy, it looks good on your resume or you think
you can make money.
Post-2000: The WWW is as ubiquitous as television was in the 80s. You're on it, or you're nobody!
How do you retrieve information from the Internet?
Use one of the (many) high-level protocols and its software user interface.
- FTP - file transfer protocol for down/up loading files
- Telnet - for login to remote hosts
- NNTP - Usenet bulletin board and news posting protocol
- SMTP - email protocol, one-to-one or one-to-many message sending
As well as Gopher, WAIS... find out what these are by doing a
little web surfing!
How is information stored on Internet computers?
There are thousands of different file formats.
A file format is a particular way of storing or ordering information in a file.
The specification of a file format includes information regarding what goes
into a file, and the order it is written/read.
GIF, PICT, PIC, PNG, RGB, SGI, TGA, BMP, PSD, RAW, SUN, TIFF... all of these
are file formats for images (and there are many, many more)!
Common file formats.
You can look up some file
formats. Here are some you might find on the web:
- PostScript / EPS
- RTF
- LaTeX
- troff
- SGML
- PDF
- Plain text
- Proprietry word-processor formats
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- AIFF - a sound file format
- GIF - an image file format
- Quicktime - a movie/video/animation file format
- VRML - Virtual Reality Markup Language file
...the list goes on and on.
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A particular file could be a:
- Word processor file (in one of numerous formats)
- Database file (in one of numerous formats)
- Graphics file (in one of the several hundred file formats)
- Sound file (in one of numerous formats)
...or almost anything else!
For every file format out there, you might need a special piece of software
just to view / hear / play / read / interpret it!
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Summary of the problems for Internet information
retrieval:
- Q. Where
do I look?
- Q. What
software do I use to look for and retrieve the files?
- Q. How do
I use that software?
- Q. What
file formats do I need to be able to interpret/decode to find the answer?
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So where does the WWW fit into all of this?
The WWW began in 1989 at CERN lab
to help simplify the retrieval of information from the net.
The idea underlying the WWW is that a user is able to transparently jump around
the global Internet retrieving information without worrying about the 4 problems
posed above.
Now, to answer the questions above...
- Q. Where do I look?
A. The WWW
The Web glosses over the hundreds of individual computers,
directories etc.
- Q. What software do
I use?
A. A Web browser
Only a single piece of software! The browser communicates
using several high-level protocols and eliminates the need to master numerous
pieces of software.
- Q. How do I use the
software (web browser)?
A. By clicking the mouse on hyperlinks
or selecting them from a menu.
What could be simpler? Previously, software was used by typing
cryptic commands into command-line user interfaces.
- Q. What file formats
do I need to decode?
A. None, the web browser handles that
for you!
The modern browser will (with the help of plugins and
helper-applications) display images, play sounds, layout text and interpret
a diversity of file formats without you needing to lift a finger!
Example Web sites
- Search engine (a good
place to begin!)
- Home page
- Business page
- Art gallery, museum or
cultural site
- Find your own sites and
look at those for exercise 1.
This lecture's key point(s):
- The WWW is a document network linked by hyperlinks.
- The WWW and Web browser mask the complexities of accessing computers and
files on the Internet and therefore...
... the WWW simplifies the task of retrieving information from remote computers.
CSE3325
courseware | CSE3325
lecture notes
©Copyright
Alan Dorin 2005