How Google WorksLisa HolmbergBibliographical Center for Researchlholmber@bcr.org

What happens when you Google?

Google Search ResultsURL, size, date last crawledCached linkPages like this oneDatabase Google UsedApproximate # of hitsAds selected by Google based on you search terms Search terms are in bold

Google Cache

Google CachedCached reveals the page as Google found itmay differ from the current pageCached exists if a page is full-text indexedAbout 1 billion pages in Google are not cachedNot fully searchableno Cached if a page owner requests not to be cached

Boolean SearchingAnd

Default AND between termsThe Fuzzy Andonly some of the words if a page is importantwords may occur only in link to the pagewords occur somewhere on the site a page belongs to

StemmingGoogle stems when appropriateIncludes plural, singular, past, present tense of words in searchSearch: school librarianResult: library, librarian, librarys, librarians

Single word searches arent stemmed

What Google doesnt search(unless you ask nicely)Common or Stop words are ignoredNo official list from GoogleAuto-phrasingSearches containing only stop words

What Google doesnt search(unless you ask nicely)

Google Search ResultsMore than 100 factors in the metricsOn-the-page metricsWord order mattersWord frequencyAutomatic-phrasingIn the title In unique fontsIn prominent areas (like lists)

PageRankOff-the-page metricsWords describing the linkLinks on one site to another are like votes-- PageRankStuffing the ballot boxReputation of the voting pageCant buy a better PageRankPageRank independent of search terms

But how do I make my searches better?

Improving Googles AND+ Inclusion operatorForce searches on stop wordsTurns off stemming

Use quotation marks for phrasespublic librarian 234,000 .4% ofpublic librarian 58,600,000 Forces searches on stop wordsTurns off stemming

Improving Googles ANDHyphen makes phrases and searches with and without hyphensbite-sized retrieves: bite-sized, bite sized, bitesized

Other examples?

Boolean SearchingOr

Not

Search OperatorsOR searchSearch for two terms at once- exclusion operatorUse with care; Search: twins Minnesota 2,750,000 Eliminate undesired wordstwins Minnesota sports 1,300,000

Search Operators* full-word wild card, word substitutionIdeal for partly remembered quotesSearching for answers to questionsProximity searches

~ synonym operator~guide searches for: tutorial, manual, help, map, tips

Limitless Options for LimitsIntitle: terms are searched for in title onlyPages concentrate on termHybrid cars intitle:mileageCombine with ORintitle:"new urbanism" OR intitle:"sustainable communitiesallintitle: Combine with site:allintitle: hybrid cars mileage site:.com

Using URLsLimit to a domain (edu, com, etc)site:edu OR site:gov OR site:lib.co.usSearch within a sitesite:memory.loc.gov dust bowlUse Google as a search engine for a siteCan ONLY use first part of URLOmit http: & final /inurl:dustbowl searches for term anywhere in URL

Finding that fileFiletype:Search for a particular type of documenttax return filetype:pdfExclude a filetype-filetype:xlsCan use view as HTMLAvoid virusesAllows you to read it even if you dont have the software

More about GoogleGoogle Guide http://www.googleguide.com/Google Librarian Center http://www.google.com/librariancenter/index.html

RECGoogle doesnt actually search the web. It searches its index of the web a copy.The doc server assembles the results that the index server produces. This is where Googles page rank software comes in to determine what order the results are in.Stress that Google is searching its database of copies of the web, spread out over 500 computers

Proof that Google is searching a database and not the real web.Googles default, but its fuzzyProblems?words can occur anywhere in results pagesmay have different meanings or contextssome pages may not contain all of your wordssome may not have any of your words

AndTalk briefly about Boolean searches (how many know what this is)

StemmingThe word is automatically searched as the stem or root with many endings allowed.kite flying retrieves words with kite kites, flying, fly, flyers, flyers, flyers--side note not case sensitive

Write in Turn off answersOperator, quotes, single word searches or searches using only stop words Write in Turn off answersOperatorQuotesSingle word

Google MetricsOver 100 different factors in each search, algorithm is always changing + spider continually updating database (thus results change)

Proprietary software

Search words can appear in title of page, link to page, URL of the page & the page itselfPages weight by prominence of words & frequency of words;Searches for all your terms on a page, even better your terms near each other best of all pages where your search terms appear in the order you typed them.Weights links pointing to the page (popularity contest doesnt return the most creditable resource)Links from more popular sites are weighted more

ReputationSome receive high rep by default, gov agencies, well-know or prominent companies, university faculty (smithsonian, nasa, JAMA)Good rep by association with the above

Use quotes or inclusion operator to turn off stemming, force search on stop words, Always use the hyphen on words that might be hyphenated since it searches both

Words are treated as a phrase simliar to w/ quotes

Other examples: asian-american, african-american, mother-in-law, ex-wife, e-mail

ORUseful when:stemming doesnt cover the variation your looking for;To cover a common misspelling;For synonyms parent/guardian;Address apostrophe variations

Can also use | instead of OR

NOTNot isnt supported by Google, will use (-) insteadWildcardRecently softened no need to use more than one asterisk per word-The parachute was invented by *- Vitamin * is good for eyes

Ask class for examples

~college~zoo~libraryOther uses?How would you use this?

Google toolbar featureHow would you use this?