Googling Google

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Class 38: Googling Cs150: Computer Science University David Evans Of Virginia Computer Http:/ / Www.cs.virginia.edu/ Evans Science Some Searches. “ David Evans” “ Dave Evans” “ Idiot” “ Lawn Lighting” Tomorrow At 6Pm ( But Google Doesn’ T Know That!) Cs150 Fall 2005: Lecture 38: Googling Google 2 Building A Web Search Engine • Database Of Web Pages – Crawling The Web Collecting Pages And Links – Indexing Them Efficiently • Responding To Searches – How To Find Documents That Match A Query – How To Rank The “ Best” Documents Cs150 Fall 2005: Lecture 38: Googling Google 3 Crawling Crawler Activeurls = [ “ Www.yahoo.com” ] While ( Len( Activeurls) > 0) : Newurls = [ ] For Url In Activeurls: Page = Downloadpage ( Url) Newurls + = Extractlinks ( Page) Activeurls = Newurls Problems: Will Keep Revisiting The Same Pages Will Take Very Long To Get A Good View Of The Web Will Annoy Web Server Admins Downloadpage And Extractlinks Must Be Very Robust Cs150 Fall 2005: Lecture 38: Googling Google 4 Crawling Crawle