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
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