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How Does Google Work? Google As a Search Engine

How Does Google Work? Google As a Search Engine

How does work? Google as a

Ethical Forum University Foundation November 2009

Vincent Blondel Louvain School of Engineering, UCL «Don’t be evil»

1998 and

1996: Research project, by Larry Page and Sergey Brin at

1998: Google Inc. company. 25 million webpages indexed.

2000: One billion webpages indexed. 2009 2004: Google goes public.

2005: One billion images.

2006: "to google" added to the Oxford English Dictionary.

PageRank 6

PageRank 5

Google employs a number of techniques to improve search quality including PageRank, , and proximity information. 6 www.google.be PageRank 10

www.uclouvain.be PageRank 9

www.kbr.be PageRank 8

www.fnrs.be PageRank 7

www.fondationuniversitaire.be PageRank 6

The web: a democracy of links http://kvina.niva.no/booking/ The web: a democracy of links

The web: a democracy of links 15 23 billions webpages

http://www.worldwidewebsize.com/ PageRank democracy: let the links vote

You webpage inherit a high PageRank if it is being pointed by pages that themselves have a high PageRank. How is this done?

• Frequent updates ()

• Storage 36 data centers (19 in the U.S., 12 in Europe). About 450.000 computers

• Sophisticated distributed computation To be googeable or not to be

Golden triangle

• Position 1: 100% • Position 2: 100% • Position 3: 100% • Position 4: 85% • Position 5: 60% • Position 6: 50% • Position 7: 50% • Position 8: 30% • Position 9: 30% • Position 10: 20% Genesis 1:1 "In the beginning God created the heaven and the earth."

Organic Search Organic Results Paid for by the owners. Sponsored Links

Google ranking robustness

From: *** From: *** Date: December 16, 2006 1:20:56 PM CST Date: December 18, 2006 6:29 To: *** • Google changes theTo: Vincent algorithm Blondel ranking Subject: google Kinderstart had a traffic 10Subject: million google a month, something caused its ranking Dear Girish, to drop. Traffic dropped 70 percent and revenue dropped 80 percent. Vincent is the person IKinderstart had mentioned whosued has Google. ceased Hi Prof. Blondel, to exist now that his webpage is no longer reachable via Google! I'm Prof. Kumar's ex-student, now working at Google. He told me about the problems you were having with your website listings under Google Can you please• Google give him a pointer removes on whom to write to? webpagessearch. It seems your site from is being searched index properly now - it shows up at the top of the results while searching for your name. I am copying him on this message. Thanks, Best, --Kumar Girish

------• P. R. Kumar Franklin W. Woeltge Professor of Electrical and Computer Engineering, and Research Professor,Google: Coordinated «miserable Science Lab failure» • Buy links 26 Email from a UCL colleague (sometime in 2007).

«Un jour, j'ai besoin du CV du recteur de l'UCL pour la soumission d'un projet. J'utilise Google et je tape "Bernard Coulie". Sans faire attention, j'entre en fait "BernardCoulie", sans espace, et je tombe sur deux liens internes à l'UCL. C'étaient deux fichiers qui donnaient les salaires de tous les membres de l'université. Par accident, ces fichiers étaient mal protégés et accessibles à tous.

J'avertis les informaticiens. Alerte générale. Durant la nuit tout est réparé.

Restaient les caches pour lesquels il a fallu contacter Google ainsi que les autres moteurs de recherche afin que l’information disparaisse totalement du web.»

Two months ago Two weeks ago Two days ago

2356300965432378987 x 577810098750098318 = ?

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