needle in the haystack - bnrgbnrg.cs.berkeley.edu/~randy/talks/saturdayclass05.pdf · the united...
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Needle in the Haystack:The Technology of Internet Search
Randy H. KatzThe United Microelectronics Corporation Distinguished Professor
Computer Science Division, EECS Department
University of California, Berkeley
Berkeley, CA 94720-1776 USA
randy@cs.Berkeley.edu 2
Outline
• Historical Background
• Information Tsunami
• Anatomy of a Web Page
• Anatomy of Web Access
• The Challenge of Search
• Google’s Page Rank Algorithm
• Fun and Games with Internet Search
• New Directions
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Search is BIG!
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And the World is Going Digital
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Outline
• Historical Background
• Information Tsunami
• Anatomy of a Web Page
• Anatomy of Web Access
• The Challenge of Search
• Google’s Page Rank Algorithm
• Fun and Games with Internet Search
• New Directions
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Historical Background:The Perfect Storm
ARPANet 1969
NSFNet 1985
Commercial Internet 1995
World Wide WebMarc AndreessenNCSA Mosaic1993
Jim ClarkNetscape1995
Vannevar Bush “As WeMay Think” MEMEX 1947
Ted Nelson Xanadu Hypertext 1965-1990Autodesk
SGML 1986
Tim Berners-Lee URL/HTTP/HTML 1989
Bill Atkinson Hypercard 1987
Est. $15.5 Billion spent on-lineThanksgivings to Xmas 2004, up 28% since 2003
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Outline
• Historical Background
• Information Tsunami
• Anatomy of a Web Page
• Anatomy of Web Access
• The Challenge of Search
• Google’s Page Rank Algorithm
• Fun and Games with Internet Search
• New Directions
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Information Tsunami
• Bit: Binary digit – either a 0 or 1• Byte: 8 bits
– 1 byte: single character– 10 bytes: a single word– 100 bytes: Telegram or punched card
• Kilobyte: 1,000 or 103 bytes– 1 kilobyte: Very short story– 2 kilobytes: Typewritten page– 10 kilobytes: Encyclopedia page– 50 kilobytes: Compressed document image page– 100 kilobytes: Low-res photo– 200 kilobytes: Box of punched cards
http://www.sims.berkeley.edu/research/projects/how-much-info/index.html
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Information Tsunami
• Megabyte: 1,000,000 or 106 bytes– 1 megabyte: Small novel or 3.5in floppy disk– 2 megabytes: Hi-res photo– 5 megabytes: Complete works of Shakespeare– 10 megabytes: Minute of hi-fi sound– 100 megabytes: 1m shelved books– 500 megabytes: CD-ROM
• Gigabyte: 1,000,000,000 or 109 bytes– 1 gigabyte: Pickup truck filled with paper– 2 gigabytes: Movie on a DVD– 50 gigabytes: Floor of books– 100 gigabytes: Floor of academic journals– 500 gigabytes: Biggest FTP site
http://www.sims.berkeley.edu/research/projects/how-much-info/index.html 10
Information Tsunami
• Terabyte: 1,000,000,000,000 or 1012 bytes – 1 terabyte: 50,000 trees made into paper and printed
or 1 day of EOS data
– 2 terabytes: Academic research library
– 10 terabytes: Printed collection of the U.S. Library of Congress
– 50 terabytes: Contents of a large mass storage system
– 400 terabytes: National Climate Data Center (NOAA) database
• Petabyte: 1,000,000,000,000,000 or 1015 bytes– 1 petabytes: 3 years of Earth Observing System (EOS) data
– 2 petabytes: All U.S. academic research libraries
– 8 petabytes: All information available on the Web
– 200 petabytes: All printed material (2001)
http://www.sims.berkeley.edu/research/projects/how-much-info/index.html
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Information Tsunami
• Exabyte: 1,000,000,000,000,000,000 or 1018 bytes– 2 exabytes: Total volume of information generated worldwide
annually
– 5 exabytes: All words ever spoken by humans
• Zettabyte: 1,000,000,000,000,000,000,000 or 1021 bytes
• Yottabyte: 1,000,000,000,000,000,000,000,000 or 1024 bytes
http://www.sims.berkeley.edu/research/projects/how-much-info/index.html 12
Outline
• Historical Background
• Information Tsunami
• Anatomy of a Web Page
• Anatomy of Web Access
• The Challenge of Search
• Google’s Page Rank Algorithm
• Fun and Games with Internet Search
• New Directions
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Anatomy of aWeb Page:
Randy’s Home Page
• URL: Uniform Resource Locator
• Images
• Text
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Anatomy of a Web Page:Randy’s Home Page
<html><head><title>Professor Randy Howard Katz University of California BerkeleyComputer Science Division Home Page</title><meta name="description“ content="Home Page of Berkeley Computer Science
Professor Randy Howard Katz"><meta name="keywords“ content="Katz Randy Howard Berkeley Professor University California Electrical Engineering Computer Science Department RAID Redundant Arrays Inexpensive Disks SPUR Snoop Wireless Communications Networks Programmable Network Elements">
</head><body><p><img height="269" src="Randy_2004.jpg" width="182" align="bottom"naturalsizeflag="0"> <img height="269" src="RHK85a.jpg"width="177" align="bottom" naturalsizeflag="0"> </p>
<p><font size="-1">2005 vs. 1985 ... The hair is grayer, but the smirkremains the same!<br><br>"... Katz, a thin, almost gaunt man with horn-rimmed glasses magnifyingsunken eyes. ..."<br>--George Johnson, WIRED Magazine, (January 2000), page
150.</font></p><p><img src="VISIONAR.JPG" align="bottom"> </p>
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• Text
• Images
• Links!
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Anatomy of a Web Page:Randy’s Web Page
<hr align="left"><h1>Professor Randy H. Katz</h1>
<h3>Electrical Engineering and Computer Science Department</h3>
<p><a href="http://www.umc.com.tw/"><img hspace="6"src="UMCLogo.gif" align="left"> </a>
<b><font size="+1">The
<a href="http://www.umc.com.tw/">United Microelectronics Corporation</a> Distinguished Professor</font></b></p>
<p><font size="-1"><br clear="left">
Ph.D., University of California, Berkeley, 1980.<br>
M.S., University of California, Berkeley, 1978.<br>
A.B., Cornell University, 1976.<br>
</font></p>
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Outline
• Historical Background
• Information Tsunami
• Anatomy of a Web Page
• Anatomy of Web Access
• The Challenge of Search
• Google’s Page Rank Algorithm
• Fun and Games with Internet Search
• New Directions
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Anatomy of Web Access
Web Browser Web Server
Web PageIn HTML
Naming System (DNS):Name-to-Address MappingIP address
Link URLhttp://www.umc.com.tw/
(1)(2)
(3)
(4)
Taiwan
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EdgeCache
Anatomy of Web AccessContent Caching
Web Browser OriginWeb Server
Web PageIn HTML
Naming System (DNS)Origin IP
Link URL…/English/about/index.asp
(5)
(6)
(7)
(8)
Content Network DNSEdge Cache IP
ContentDistribution
Taiwan
San Jose
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Outline
• Historical Background
• Information Tsunami
• Anatomy of a Web Page
• Anatomy of Web Access
• The Challenge of Search
• Google’s Page Rank Algorithm
• Fun and Games with Internet Search
• New Directions
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Challenges of Search
• How to find all the pages on the Web?• How to order the pages by relevance?• How to make searchable the content on those pages?• How to keep it all up-to-date?
• Web Crawlers/SpiderBots– Network software executing in parallel that follow links in the
Web to find content– Web pages “scraped” for more links follow– Web revisited on the order of once every two-three days
• Indexers– Web pages “scraped” for search terms to build indexes– (Google) Page rank algorithm: order a page within the index based
(roughly) on how many pages refer to it 22
Quick (and Incomplete) History of Search Engines
UMinnVeronica &
Archieservices
for gopher &
ftp
MITWandex/WWW
Wanderer
Aliweb
CMULycos
1st Commercial Search Engine
StanfordYahoo!
DirectoriesBattle for Popularity: Webcrawler (UWash)
HotBot (Wired)Excite (Stanford) Infoseek (ABC)
Inktomi (Berkeley) AltaVista (DEC)
Google (Stanford)
Yahoo! acquires Inktomi
Yahoo! acquires Overture
(AlltheWeb, AltaVista)
1993 1995 1997 1999 2001 2003Pre-Web 2005
Yahoo! deploys
jointtechnology
a9.comAlltheWebAsk Jeeves
ClustyGigablastEz2FindTeoma
WiseNutGoHookWalhelloKartoo
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Search Challenges and Issues
• Web growing faster than search engines can index• Web pages updated frequently, forcing frequent
revisits • Key word only searches results in many false positives• Difficult to index dynamically generated sites: the so-
called “invisible web”• Some search engines order results by financial
“placement” considerations rather than relevance• Some sites trick search engine to display them first
for some keywords—results in polluted search results, with more relevant links pushed down among the results
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Outline
• Historical Background
• Information Tsunami
• Anatomy of a Web Page
• Anatomy of Web Access
• The Challenge of Search
• Google’s Page Rank Algorithm
• Fun and Games with Internet Search
• New Directions
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Page Ranking Algorithms
• Web page relevancy– Many hits, how to insure the best/most relevant web
pages are presented first in answer to a search
• Location and Frequency of Keywords– Index terms in page title raise its relevance for that term
– Keywords near “top” of page more relevant than bottom
– High keyword frequency boosts relevance
• If search engine strategy is known, page developers will “game” the strategy to get their pages ranked higher
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Google’s Page Rank Algorithm
• Which is the most important page?
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Google’s Page Rank Algorithm
• Googlese from their web page:– PageRank relies on the uniquely democratic
nature of the web by using its vast link structure as an indicator of an individual page's value. Google interprets a link from page A to page B as a vote, by page A, for page B. But, Google looks at more than the sheer volume of votes, or links a page receives; it also analyzes the page that casts the vote. Votes cast by pages that are themselves "important" weigh more heavily and help to make other pages "important.”
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Google Page Rank Algorithm
• Basic idea:– Page’s rank determined by the number of links to the page (also known
as citations)– If citing page is more important (has a high page rank/authority page)
then the pages it cites are more important– If citing page has many links, then cited page is less important
(normalize for number of links on citing page)
PR(P) is page rank of page P, T1, …, T
Nare pages that cite P,
C(P) is the # links from Page P, D is a “decay factor”, e.g., 0.85then:
PR(P) = (1 – d) + d (PR(T1)/C(T
1) + … + PR(T
n)/C(T
n))
• See http://www-db.stanford.edu/~backrub/google.html
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GoogleConceptual
Architecture
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Google Server Architecture
• Index servers: search term partitioned and mapped to doc list
• Intersect to find document list, sort by page rank
• Document IDs used to extract text from Doc Servers
• Over 100,000 processors (and growing) in Googleplex
GoogleWeb Server
Spell Checker
Ad Server
Doc ServerDoc Server
Doc ServerDoc Server
Doc Server
Doc ServerDoc Server
Doc ServerDoc ServerIndex Server
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Outline
• Historical Background
• Information Tsunami
• Anatomy of a Web Page
• Anatomy of Web Access
• The Challenge of Search
• Google’s Page Rank Algorithm
• Fun and Games with Internet Search
• New Directions
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Fun and Games
• Google Scholar
• Googling Someone
• Google News
• Comparison Shopping
• Google Whacks
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Google Scholar
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Google Randy
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Google Randy Katz “Google Index”
AdvertisingPlacement
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Google News
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Comparison Shopping
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elgooG
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Google Whacks
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Business ModelAd Placement and Click-Thru
Old data (2002): Google is now market leader in ad revenue2004 revenue through 9/30/04: $2.1B
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Outline
• Historical Background
• Information Tsunami
• Anatomy of a Web Page
• Anatomy of Web Access
• The Challenge of Search
• Google’s Page Rank Algorithm
• Fun and Games with Internet Search
• New Directions
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Top 10 Search Engines
10. DMOZ.org9. Alltheweb.com8. KartOO.com7. MSN.com6. Dogpile.com5. AskJeeves.com4. About.com2. Yahoo.com2. Vivismio.com1. Google.com
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Clustering
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Google Video Search
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Google Video Search
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Amazon’s A9
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Amazon’s A9
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A9’s Yellow Pages
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A9’s Yellow Pages
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Innovations Now andYet to Come
• Index ever larger portions of the Web, even beyond traditional web pages, e.g., video
• Better quality/higher relevance searches
• Better presentation of results, e.g., clustering, site information
• Better exploitation of semantic relationships for improved page ranking, more personalization, e.g., user’s zip code
• More services (Web, news groups, blogs, comparison shopping, video/audio, yellow pages, etc.)
• Integrate with desktop machine
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Parting Thoughts
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Parting Thoughts
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“Where is the wisdom we have lost in knowledge?Where is the knowledge we have lost in information?”
T.S. Eliot, “Choruses from the rock”, Selected Poems, NY: Harvest / Harcourt, 1962, p. 107.
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Needle in the Haystack: The Technology of Internet Search
Thanks for Your Patience & Attention!Questions?
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