《信息科学类专业英语》课件第15章

Lesson15HowDoSearchEnginesWork?

(第十五课搜索引擎如何工作？)

Vocabulary(词汇)ImportantSentences(重点句)Multiple-choiceQuestion(多选题)

Problems(问题)

Oneofthebiggestreasonswhymanyorganizationsarenotdoingevensimplethingstohelppeoplefindtheirwebsitesinsearchenginesistheysimplydon’tunderstandhowsearchengineswork.Thisarticleisintendedtoexplainthebasicsofhowsearchenginesworkandinthecourseofdoingsoshattersomesearchenginemythsandhelpyouunderstandwhatyoucandotohelppeoplefindyourwebsiteinsearchengines.1WhatisaSearchEngine?

Thefirsttosteptounderstandinghowsearchenginesworkistounderstandwhatasearchengineis.Thesimplestexplanationisthatsearchengineisatoolforfindingthingsonline.Therearemanydifferenttypesofsearchenginesbuttheycanbeputintotwomajorcategories.

1.1Human-PoweredDirectories

Thefirst“searchengines”werenotactuallysearchenginesaswethinkofthemtoday,butsearchabledirectoriesofwebsitesorganizedbyhierarchicalcategories.Asiteisaddedtoadirectorywhenthewebsiteownerfillsoutasubmissionformonthedirectory’swebsiterequestingtheirsitebeincludedinthedirectoryandincludetheirwebsite’stitle,description,URL(webaddress),andcategory.Amoderatorlaterreviewsthesiteandifitmeetsthedirectory’scriteriaalistingforthatsiteisaddedoractivated.TheoriginalYahoowasoriginallyahuman-powereddirectory,anddirectorieslikeOpenDirectoryProjectcontinueontoday.

Thedownsideofthehuman-poweredsearchengineisthatitonlyincludeswebsitesthathavebeensubmittedtoit,whichmeansyoumaynotfindwhatyou’relookingforespeciallyifit’sanewwebpage.[1]Theotherdownsidefromthedirectories’pointofviewisthatreviewingeverysitesubmittedisverylabor-intensiveandcostly.Iknowbecausemycompany’s“searchengine”,OurChurch.Com’sDirectoryofChristianWebsites,likealmostallchurch/Christian“searchengines”,isahuman-powereddirectory.

1.2Crawler/Spider-PoweredSearchEngines

Thenextgenerationofsearchengineshasprogramswhichactivelyseekoutnewsitesandreadthemintotheirindexes.Theseprogramsarecalledcrawlers,spiders,robots,orbots.Alloflargestandmostpopularsearchenginestodayareofthistype,includingGoogle,Yahoo,MSN,andAsk.Therestofthisarticleisfocusedonhowthesecrawler/spider-poweredsearchenginesworkbecausemorethan99%ofsearchesaredoneonthistypeofsearchengine.2TheCrawler

(1) Searchbotsperiodicallyrereadeverywebpageintheirdatabase.Whydoesthismatter?

Youdon’thavetodoanythingwhenyouchangeyoursite.Ifyoursiteisalreadylistedinasearchengineandyoumakechangestoyourwebsite,searchengineswilleventuallyupdatetheirinformation.

Youdohavetobepatient.Thefrequencyofre-crawlingvariesdependingonthesearchengine,theimportanceofyoursite(asdeterminedbythesearchengines),andhowoftenyouupdateit.Itcouldtakeadayoritcouldtakemorethanaweek.

(2) Searchbotsfollowlinksonthepagesthathavealreadybeencrawledinordertofindnewpages.Whydoesthismatter?

Ifyouaddanewpagetoyourwebsiteorcreateanewwebsite,it’simportanttoaddalinktoitonawebpagethatisalreadyinthesearchengines.

Ifawebpagethatisalreadyinthesearchengineshasalinktoyournewpageornewwebsite,youdonotneedtosubmitarequesttothesearchenginestocrawlthenewpageorwebsite,thoughitmaystillbeworthdoingjusttobesureyourwebsitewillbefoundquickly.

(3) Somesearchengineshaveformsyoucansubmittorequestawebsitebecrawled.Whydoesthismatter?

Ifyouhaveanewwebsiteandnositeslinktoit,searchbotswillnotbeabletofindit.Inthiscase,submittingaformtothesearchenginerequestingyoursitebelistedorindexedcangetitintosearchengines.

Becausehuman-powereddirectoriesdonothavesearchbots/crawlers,tobelistedinthemyoumustsubmitarequestform.[2]

2.1TheRankingAlgorithm

Sometimeafterawebpagehasbeencrawledbythesearchbotorcrawler,thesearchenginethenprocessesorindexesthepagetodeterminewhatsearchwordsandphrasesthepageisrelevanttoaswellashowrelevantthatpageiscomparedwithotherwebpagesforthosephrases.Duringthisprocessingthesearchenginelooksatmanydifferentfactorsincludinghowmanytimeseachwordandphraseoccursonthepage,whichwordsareinheadingsorbold,thedomainnameofthesite,filenameofthepage,thepagesthatlinktothepage,andmanymore.

Exactlywhichfactorsasearchenginelooksatandhowthey’reweightediscalledthesearchengine’ssearchrankingalgorithm.[3]It’slikethesearchengine’s“secretsauce.”Eachsearchengine’salgorithmisdifferentandeachisaheavilyguardedsecret.

Whydoesthismatter?

Thereistimebetweenwhenyoursiteiscrawled(orrecrawled)andwhenitisprocessedorindexed.So,itcantakeaslittleasafewhourstomanydaysorweeksbeforechangestoyourwebsitemayproducechangesinitssearchrankings.

Becauseeachsearchengine’srankingalgorithmisdifferent,awebpagecanbe#1inGooglebut#20inYahooforaparticularphrase.

Becauseeachsearchalgorithmisaheavilyguardedsecretnobodyoutsideofafewselectengineersateachsearchengineknowsexactlyhowmucheachparticularfactorweighsintotherankingsofeachsearchengine.But,peoplewhospendtheirprofessionalliveshelpingsitesrankbetterinsearchengineshavegainedverygoodideaastowhatfactorsmattermost.

Becausethesearchrankingalgorithmslookattext,headings,andotherelementsonawebpage,changingthingsonthewebpagecanchangewherethatwebpageappearsinthesearchresults.

Searchrankingalgorithmslookatfactorsoutsideofawebpage,suchastheageofawebsiteandlinkstothewebpage.So,thereareotherfactorswhichyoumayhavelessinfluenceover.

Thegoalofeverysearchengineistodisplaytotheusertheinformationorwebsitestheuserislookingfor.Inotherwordseverysearchenginewantstoprovidethebest,mostrelevantresults.Asaresult,searchenginesareconstantlyimprovingtheiralgorithmsandincludingnewfactorswhichtheythinkwillproducebettersearchresults.[4]Whydoesthismatter?Assearchalgorithmschange,sowillyourwebsite’ssearchenginerankings.

2.2TheSearchEngineResultsPages(SERPs)

Thecrawlingofwebsitesandindexingofwebpagesareconstantlygoingonevenwhennooneissearching.Thelastpartinthesearchprocessispartthatyou’reprobablymostfamiliarwith–theactualsearch.Youtypeinaword,shortphrase,orquestion,andthesearchenginedisplaysalistofwebsites.ThatlistofwebsitesiscalledthesearchengineresultspageandsometimesreferredtoastheSERPs.IfyoudoasearchandlookattheSERP,you’llnoticetwocolumns.Abovetherightcolumnitsays“SponsoredLinks”.Thesearepaidadvertisements.ThecompaniesandorganizationslistedherepayafeetoGoogleforeachpersonwhoclickstheirad,sothey’reoftenreferredtoasPay-Per-ClickorPPCads.Intheleftcolumnaretheunpaidsearchresultsalsosometimescalledtheorganicresultsornaturalresults.Thesearethewebsitesthesearchenginebelievesaremostrelevanttothesearchphrasethatwasqueried.Sometimessearchenginesalsodisplaysponsoredlinksintheleftcolumnabovethenaturalresultsorwillevenplaceablockofpay-per-clickadsinthemiddleofthenaturalresults.Sponsoredlinksarealwayslabeled,thoughnotalwaysveryclearly.3WhydoesthisMatter?

Fromthesearcher’sperspective,thereisnothingwrongwithclickingonapaidlink.Youmayfindwhatyou’relookingforthere.Butit’simportanttobeawareofwhichwebsitespaidtobeintheresultsandwhicharetherenaturally.

Fromthewebadministrator’sperspective,it’simportanttounderstandtherearetwoopportunitiestogettothetopofthesearchenginerankings,throughnaturalresultsandbypurchasingpay-per-clickadvertising.4HelptheSearchEngines

Withabetterunderstandinghowsearchengineswork,youcanmakebetterdecisionsaboutthemarketingofyourwebsitethoughsearchengines.Searchenginesneedyourhelptofindyourwebsiteandtoknowwhatwordsandphrasesit’srelevantfor.Givethemthehelptheyneed.That’swheresearchengineoptimizationcomesin,butI’llgettothatonanotherday.1. enginen.发动机,引擎。

2. hierarchicaladj.分等级的。

3. downsideadj.下降趋势的。

4. algorithmn.运算法则。

5. botn.robot的缩写。Vocabulary

[1]Thedownsideofthehuman-poweredsearchengineisthatitonlyincludeswebsitesthathavebeensubmittedtoit,whichmeansyoumaynotfindwhatyou’relookingforespeciallyifit’sanewwebpage.

人力搜索引擎的崩溃在于它只包含已经被提交的网站，这意味着你不可能查询到你想要的东西，尤其是在搜索新网页的情况下。句中的第一个that引导表语从句，第二个that引导的从句作为定语从句修饰websites。关系代词which在从句中作主语。ImportantSentences

[2]Becausehuman-powereddirectoriesdonothavesearchbots/crawlers,tobelistedinthemyoumustsubmitarequestform.

因为人力文件夹没有被列出的搜索机器人(爬行者)，因此你必须提交一个请求表格。句中because引导原因状语从句，tobelistedinthem作为定语修饰bots/crawlers。

[3]Exactlywhichfactorsasearchenginelooksatandhowthey’reweightediscalledthesearchengine’ssearchrankingalgorithm.

实际上搜索引擎关注哪些因素以及这些因素的比重被称为搜索引擎的搜索等级算法。句中which和how引导的从句是两个并列的主语从句。

[4]Asaresult,searchenginesareconstantlyimprovingtheiralgorithmsandincludingnewfactorswhichtheythinkwillproducebettersearchresults.

结果，搜索引擎一直在改善它们的算法并且包含它们所能想到的新的因素，这一切将产生更好的搜索结果。句中whichtheythink作为定语从句修饰factors，整个句子的主语由一个主语从句来表示。

(1) Accordingtothearticle,whataremajorcategoriesofsearchengi