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19 Search Engines 19 Search Engines • We all use search engines every day • But could you explain what happens behind the scenes? • That’s what you could be asked about in the exam • So we’ll look at how search engines work • For a start, we’ll focus on the basic process… 19 Search Engines How Search Engines Work You need to know about three stages… Client Side Server Side Stage One Stage Three Stage Two Web Server Database 19 Search Engines How Search Engines Work Stage One: Client Side You type keywords in the box & then click the button to Search Stage Two: Server Side The search engine uses its own database to find matches with your keywords Stage Three Client Side The results are displayed on your screen 19 Search Engines How Search Engines Work • We all obviously know about stages 1 and 3 • That’s because we see that happening on our client devices • But we don’t see what happens on the server side • So we’ll now focus on what happens behind the scenes with search engines Search engines store info about billions of web pages… 19 Search Engines But it’s all HTML code that contains details for each All those details are stored in the database called anpage Index Server Side Web Server Database Index To collect all that data earch engines use special programs 19 Search Engines They are called spiders because the ‘crawl’ the Web… The spiders send back the details to store in the Index… Server Side Web Server Database Index 19 Search Engines How Search Engines Work • So…search engines use special programs called spiders or web crawlers or bots • They ‘crawl’ or visit billions of sites and save copies of all the pages • All that data is sent back and stored in a special database called an index • Each search engine had its own spider programs & its own index • That’s why they give different results! 19 Search Engines How Google Works http://www.youtube.com/watch?v=BNHR6IQJGZs 19 Search Engines 19 Search Engines • Now we’ll focus on how people actually search • That means the keywords you type into the search box • And also some special techniques you can use to make searches smarter • Let’s start with a reminder of how keywords fit into the search process… 19 Search Engines Using Keywords Client Side Server Side Web Server keywords Database Index 19 Search Engines Using Keywords • On the client side, we enter keywords • Your keywords are then sent across to the server side • Your keywords are compared with the Index database • Back on the client, you get the results • But you can get better results if you use some smart search techniques • These include using quotes, minus, star and the word OR… 19 Search Engines Use quotes to match exact phrase or quote “ ” Use minus to exclude words from search jaguar -car Use * as a ‘wildcard’ to get variations of a word *plastic Use OR to get results with both words chimp OR gorilla 19 Search Engines 19 Search Engines
