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1、LinkAnalysis1RoadmapIntroductionSocialnetworkanalysisPageRankHITSSummary2IntroductionEarlysearchenginesmainlycomparecontentsimilarityofthequeryandtheindexedpages.I.e.,Theyuseinformationretrievalmethods,cosine,TF-IDF,...From1996,itbecameclearthatcontent
2、similarityalonewasnolongersufficient.Thenumberofpagesgrewrapidlyinthemid-late1990’s.Try“classificationtechnique”,Googleestimates:10millionrelevantpages.Howtochooseonly30-40pagesandrankthemsuitablytopresenttotheuser?Contentsimilarityiseasilyspammed.Apag
3、eownercanrepeatsomewordsandaddmanyrelatedwordstoboosttherankingsofhispagesand/ortomakethepagesrelevanttoalargenumberofqueries.3Introduction(cont…)Startingaround1996,researchersbegantoworkontheproblem.Theyresorttohyperlinks.InFeb,1997,YanhongLi(ScotchPl
4、ains,NJ)filedahyperlinkbasedsearchpatent.Themethoduseswordsinanchortextofhyperlinks.Webpagesontheotherhandareconnectedthroughhyperlinks,whichcarryimportantinformation.Somehyperlinks:organizeinformationatthesamesite.Otherhyperlinks:pointtopagesfromother
5、Websites.Suchout-goinghyperlinksoftenindicateanimplicitconveyanceofauthoritytothepagesbeingpointedto.Thosepagesthatarepointedtobymanyotherpagesarelikelytocontainauthoritativeinformation.4Introduction(cont…)During1997-1998,twomostinfluentialhyperlinkbas
6、edsearchalgorithmsPageRankandHITSwerereported.Bothalgorithmsarerelatedtosocialnetworks.TheyexploitthehyperlinksoftheWebtorankpagesaccordingtotheirlevelsof“prestige”or“authority”.HITS:JonKleinberg(CornelUniversity),atNinthAnnualACM-SIAMSymposiumonDiscre
7、teAlgorithms,January1998PageRank:SergeyBrinandLarryPage,PhDstudentsfromStanfordUniversity,atSeventhInternationalWorldWideWebConference(WWW7)inApril,1998.PageRankpowerstheGooglesearchengine.“StanfordUniversity”thegreat!Google:SergeyBrinandLarryPage(PhDc
8、andidatesinCS)Yahoo!:JerryYangandDavidFilo(PhDcandidatesinEE)HP,Sun,Cisco,…5Introduction(cont…)Apartfromsearchranking,hyperlinksarealsousefulforfindingWebcommunities.AWebcommunityisaclusterofdenselylinkedpagesrepresentingagroupofpeoplew
