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Information Consumers. Computer Science 01i Introduction to the Internet Neal Sample 20 February 2001. We will talk about. HTML odds and ends Internet Service Providers Networks Connections Searching Portals. Some HTML Tidbits. Changing fonts - PowerPoint PPT Presentation
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Information Consumers
Computer Science 01iIntroduction to the Internet
Neal Sample20 February 2001
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We will talk about...
• HTML odds and ends• Internet Service Providers• Networks Connections• Searching• Portals
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Some HTML Tidbits
• Changing fonts<font face=“Helvetica, Courier, Arial” size=+2>
• Changing colors<font color=RED>
<font color=#FFFFFF>
• Changing background images<body background=“background.jpg”>
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Tables
• Basic Tables<table border=“3”> table <tr> row <td bgcolor=“red”>Hi!</td>data (aka “cell”) <td>Bye!</td> </tr></table>
• Wide Cells<td colspan=“2”>This is a double-wide cell</td>
• Tall Cells<td rowspan=“2”>This is a double-tall cell</td>
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View HTML Source!
• In Microsoft Internet Explorer: right-click on a web page select “view source”or select “View” from the toolbar then “source”
• In Netscape, same process
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Internet Service Providers (ISPs)
• Connect isolated machines to the Internet
• On campus, Stanford is your “ISP” one of the best you’ll ever have =)
• Thousands of them out there Big ones with portals and content, like AOL Hackers providing dial-up shell accounts
out of the spare bedroom (www.lariat.org)
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Picking an ISP
• What is your user profile?• What is its pricing structure, flat or usage?• What speed modems does it support?• Is it Mac or Unix friendly?• What support options are there?• Does it offer web-hosting? Shell accounts?• What do your friends say?
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Consumer Grade Connections
• Modem 56 Kilobits per second/high latency Free - $20 per month
• Cable modem: 128 Kilobits per second (and up) $30+ per month, plus hardware and setup
• Cellular Modem 128 Kilobits per second/high latency $20+ per month, plus hardware But mobile!
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High-End/Small Office Connections
• Integrated Services Digital Network (ISDN)• 128 Kilobits per second/low latency• $40 per month plus hardware• Requires new phone line in your home• Share voice and data over the same line
• Digital Subscriber Line (DSL)• Up to 7 megabits per second downstream, 680
Kilobits per second upstream/low latency• $40-$250 per month plus hardware• Normal phone lines
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Industrial Strength Connections
• T1 line• 1536 Kilobits per second/extremely low
latency• < $750 per month, plus installation,
router and hardware
• T3 line• 44.7 megabits per second/extremely low
latency• Negotiated pricing, < $10,000+ per month• Stanford has one (+ an “I2 connection”)
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The challenge for a Web Consumer:
Navigation:“How do I find my way around the
web?”
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Web Navigation
• How can structure be imposed over all the information out on the web? Bookmarks Pages of links Searching Portals Rings
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Bookmarks
• Avantages• Convenient• Structure added by the consumer• Take you directly where you want to go• Always customized properly
• Disadvantages• Can only bookmark where you’ve been• Not dynamic• Easily get disorganized themselves• Not accessible from any machine?
(www.mybookmarks.com)
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Links Pages
• Advantages More easily organized than bookmarks Someone else usually does them Available anywhere (if you can remember)
• Disadvantages Rely on gatekeepers for content, updates
• can be done on your own, hard to maintain
Still have to find them (www.yahoo.com)
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Search Engines
• Allow searches over the text on the web
• AltaVista, goto.com, Lycos, Hotbot, NetFind, WebCrawler, WebDirectory, Infoseek, etc…
• Another search engine appears almost every day
• Heavily automated
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How to Search the Web
• Go to your search engine• Type in your query
Different search engines have different search syntaxes and different strengths
It is very worth it to get to know the lower level syntax of a search engine or two
• The search engine checks its index of the web for hits and returns the results
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How a search engine works
• Really a collection of several programs on several computers Information gathering programs Database programs Information serving programs
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Information Gatherer
• Automatically browses the web via “web crawling”
• Indexes each page as it is found• Stores the index in a database• What if there isn’t a link to a page?
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Database Program
• Manages many gigabytes of data• Needs to “age” data properly• Must be able to return very small
bits of data very quickly• Runs on big machines optimized for
input and output
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Information Serving Program
• Often called the “front end” of the database
• Searches the content with sophisticated matching algorithms
• Order the results with sophisticated ordering algorithms
• Formats the results into an HTML page• Hands off the page to a web-server which
returns the query
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Search Engine Advantages
• Examines large parts of the web very quickly
• Gives a good “first cut” at what is out there
• Really the only way to find most of what is out there
• Site search engines can actually be pretty good (custom software)
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Search Engine Disadvantages
• “Sophisticated” algorithms usually aren’t sophisticated enough
• Intelligent natural-language understanding is not well understood in the CS world
• 1) makes queries harder, 2) no “semantic” web
• False positives and false negatives. Many don’t have useful feedback features
• Effective, narrow searches are usually more inconvenient than a shotgun search and human skimming
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Meta Search Engines
• A search engine that queries other search engines
• Return results from several search engines
• Have a great future?• Apple’s Sherlock, others coming
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Deja News
• www.dejanews.com• A searchable archive of newsgroups• Very valuable resource
You can get your questions answered by the newsgroups without ever even posting
Content of the newsgroups is often quite different than the web.
More conversational, more informal.
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Web Portals
• Starting places on the web• Excite, Yahoo, AOL,
Netscape’s Home Page…• A new one pops up almost every day• Organize the web into various
categories and thereby impose structure on the web site reviews and categorization search engine usually built in
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More about Web Portals
• Some customization possible -- nice• Often provide teasers that are interesting• Really a play to get eyeballs for
advertisers• Human intensive, hard to automate site
As smart as computers seem, there is still no substitute for humans making decisions
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Web Portals
• Advantages provide good organization good news sources eliminate crummy websites from
consideration
• Disadvantages gatekeepers and judgment calls organization still isn’t quite there commercial motives affect content
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Sources and Further Reading
• Picking an ISP http://www.paintstore.com/coffeepot/column/
2.html
• Network Connections http://www.brandx.net/help/selecting-data-
services.html http://www.ifl.net/support/help.html
• Search Engines http://www.searchengineguide.org/cosa.htm
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Project: Formica Poodles
• We’re playing a search-engine game to find something out about the words on the web.
• Use www.altavista.com: +word1 +word2• Scoring?
2 x Count1 x Count2---------------------------(Count1 + Count2) * NumHits
• Fabulous Prizes!
• www-db.stanford.edu/~nsample/cs01/score.html
