Hyper search ing the Web Soumen Chakrabarti, Byron Dom, S. Ravi Kumar, Prabhakar Raghavan, Sridhar Rajagopalan, Andrew Tomkins Jacob Kalakal Joseph CS 572 (Spring 2011) | Class Presentation | June 21, 2011
Outline Characteristics of the WWW Motivation for building search engines Traditional SEs and the challenges Improvements the associated problems CLEVER Power of hyperlinks Hubs and Authorities Algorithm Evaluate CLEVER Future scope Answer questions and class discussion CS572-Joseph 2 June 21, 2011
WWW ~ Universe CS572-Joseph 3 June 21, 2011
Motivation for search engines CS572-Joseph 4 June 21, 2011
Initial Attempts Ranking functions based on simple heuristics CS572-Joseph 5 June 21, 2011
Challenges: Synonymy CS572-Joseph 6 June 21, 2011
Challenges: Polysemy CS572-Joseph 7 June 21, 2011
Challenges: Spamming Cheap airtickets Cheap airtickets Cheap airtickets Cheap airtickets Cheap airtickets White font on White background CS572-Joseph 8 June 21, 2011
Improvements Semantic NetworksHuman selectors Helps synonymy but worsens polysemy Impractical CS572-Joseph9June 21, 2011
Hyperlinks - What a CLEVER idea! CS572-Joseph 10 June 21, 2011
Hubs & Authorities CS572-Joseph 11 June 21, 2011
How it works CS572-Joseph 12 June 21, 2011
Clever vs. Google Googles faster!Clever looks back also CS572-Joseph13June 21, 2011
Pros Rapid convergence (5 iterations for root set of 3000 pages) Independent of the initial H, A scores Get info even before we actually crawl CS572-Joseph 14 June 21, 2011
Segregation of web into clusters CS572-Joseph 15 June 21, 2011
Cons The underlying assumption – Web links confer authority – could be incorrect! – Navigation – Advertisement – Disapproval CS572-Joseph 16 June 21, 2011
Cons Ignores the Anchor text It is not necessary for every page to be either a hub or an authority Universally popular Websites like Wikipedia will be an authority on almost everything May return a General result for a Narrow topic search CS572-Joseph 17 June 21, 2011
Whats next? CS572-Joseph 18 June 21, 2011
References S. Chakrabarti, B. Dom, D. Gibson, J. Kleinberg, S.R. Kumar, P. Raghavan, S. Rajagopalan, A. Tomkins,Hypersearching the Web. Scientific American, June 1999.Hypersearching the Web CLEVER project ( J. Kleinberg.Authoritative sources in a hyperlinked environment. Proc. 9th ACM-SIAM Symposium on Discrete Algorithms, 1998Authoritative sources in a hyperlinked environment S. Brin, L. Page. The anatomy of a large-scale hypertextual Web search engine. Computer Networks and ISDN Systems. Vol. 30, No. 1-7, pp , 1998.The anatomy of a large-scale hypertextual Web search engine WordNet Project ( CS572-Joseph 19 June 21, 2011
Group Discussion CS572-Joseph 20 June 21, 2011