Digital Media

Dr. Jim Rowan

ITEC 2110

The Internet

your computer

DHCP:

your browser(Safari)(client)

webpagesand

other stuffyahoo.com

(server)235.01.30.564

walmart.com(server)

100.43.153.07

Data Name System (DNS)

yahoo.com(server)

235.01.30.564

The Internet

walmart.com(server)

100.43.153.07

ISP

DHCP: 135.10.34.443

your computer

your browser(Safari)(client)

webpagesand

other stuff

Data Name System (DNS)

yahoo.com(server)

235.01.30.564

The Internet

walmart.com(server)

100.43.153.07

DHCP: 135.10.34.443

your computer

your browser(Safari)(client) http://www.yahoo.com

Data Name System (DNS)http://www.yahoo.com =235.01.30.564

webpagesand

other stuff

yahoo.com(server)

235.01.30.564

The Internet

walmart.com(server)

100.43.153.07

/index.html

DHCP: 135.10.34.443

your computer

your browser(Safari)(client) http://www.yahoo.com

Data Name System (DNS)http://www.yahoo.com =235.01.30.564

webpagesand

other stuff

How to start a website

• You have to buy a Domain Name– register.com– godaddy.com

• The Domain Name supplier– pay by the year– may provide some storage space for your web

pages using their IP– probably get email accounts with it– will allow you to configure your site

• set up domain-name-to-IP mapping

Let’s look at LINKS

notice that the links are distinguished from regular text (underlined and color)

also... once used, they turn a different color

here the nodes connected by links are only 1 level deep...

4-5 is usually the deepest that is recommended

more LINKS...

between pages

into pages

within pages

Disorientation..• Where am I?

– URL is SOMETIMES useful... Example:• http://www.pondliner.com/• http://www.pondliner.com/index.html• http://www.pondliner.com/PontecKits.htm

– Why just sometimes?• dynamically generated content like PHP, Perl, CGI• webpage can be different each time you visit it

• Where was I?– browsers have “back” buttons– pages can have embedded links that take you back– browser history works without user interaction– browser bookmarks work with user interaction– use search engine and remember search strings

Finding your way around...

• Bookmarks User-built– indices and links can be built by hand– people search the web and keep useful indexes

making them part of the site– may rely on the user to search and rate sites

• Indices Machine-built– indices and links are built using spiders, robots or

WebCrawlers– these are programs that search the web looking

for content

WebCrawlers

• Once looked and collected email addresses to sell to spammers

• Simple to do– request a page– look through the text of the page for something @

something.something

• Can be defeated by using unfriendly-to-robot-code like: jrowan (at) GGC (dot) USG (dot) EDU– humans can read this just fine!

Search Engines

• Search web pages looking for keywords• Then they build a catalog of keywords

– You enter a keyword in the engine– It looks at its table– It sends you the URLs associated with the

keyword

• GOOGLE extends this by including the number of links that point to that particular page

Web Protocols• Protocols define the rules to be followed in a conversation

– who talks first– what is acceptable to request– what are acceptable responses to a request– syntax is the actual form of each interaction

• HTTP - Hyper Text Transfer Protocol– identifies it as a web page request

• FTP - File Transfer Protocol– identifies it as a file that needs to be downloaded

• SMTP - Simple Mail Transport Protocol– identifies it as pertaining to email

Parts of the URL

• Has three parts:– Specifies the protocol to use

• HTTP• FTP• SMTP

– The Domain Name• www.ggc.usg.edu

– Other defining stuff• directory info and pages• data to be handed to a program

HTTP://www.jimrowan.com www.jimrowan.com/about/-can have two responses-assumes index.html yielding web page-assumes you want a directory list yielding a list of the contents of the directory:

CV.htmlindex.htmlpublications.html

www.jimrowan.com/about/index.htmlwww.jimrowan.com/about/research.html

www.jimrowan.com/about/before1990/index.htmlwww.jimrowan.com/about/after1990/index.html

Other defining stuff... directory info and pages

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=260182066605&ssPageName=ADME:X:AAQ:MOTORS:1123

http://www.almanac.com/weatherhistory/oneday.php?number=747808&wban=99999&day=31&month=3&year=2008&searchtype=zip

http://www.google.com/search?hl=en&q=tim+berners-lee&btnG=Google+Search

Other defining stuff...data to be handed to a program

And now for a little history...

A brief history

• Tim Berners-Lee (not al gore)– invented the internet – 1980 built the first web server– mid 1980s worked with hypertext– 1988- “I just had to take the hypertext idea and connect

it to the TCP and DNS ideas and ta-da! the World Wide Web!”

– wrote the first web browser (the client)

• Command driven computer interface

• GUI– Alan Kay

• GUI– Alan Kay XEROX PARC 1970’s

• GUI– Alan Kay XEROX PARC 1970’s– Steven Jobs Macintosh 1984

Outside Reading

• http://en.wikipedia.org/wiki/Web_crawlers• http://en.wikipedia.org/wiki/GUI• http://en.wikipedia.org/wiki/PHP• http://en.wikipedia.org/wiki/Cgi_script• http://en.wikipedia.org/wiki/Perl• http://en.wikipedia.org/wiki/Tim_Berners-Lee• http://en.wikipedia.org/wiki/Alan_Kay• http://en.wikiquote.org/wiki/Alan_Kay• http://en.wikipedia.org/wiki/Copyright• http://en.wikipedia.org/wiki/Fair_use• http://en.wikipedia.org/wiki/Digital_Millennium_Copyright_Act