Library Tutorial - Internet Resources - Search Engines

What is a search engine?

Browsers can go to a site if you type in the URL or click on a link within a page, but they don't know how to find pages on their own. For this task, you need a search engine. Search engines use programs called "spiders" or "robots" which spend all of their time exploring the Web. When the spider finds a Web page, it sends the URL and information about the site back to a database. When you use a search engine, you are searching that database of collected Web pages, not the Web itself. No search engine has indexed the entire World Wide Web.

When you use a search engine, you are conducting a keyword search of its database. The search engine will try to find Web pages with the exact words you type into its search box. It cannot tell the difference between "depression" (mental condition) and "depression" (American history). Keyword searches are best used when you are searching for a particular fact or piece of information.

Many search engines, including Google and Yahoo, include a directory section. Rather than having computer programs search the Web, humans look for sites. When they find a new one, they summarize it and then classify it under a subject heading. This is a good way to find information about a topic as all sites on a certain subject are grouped together.

If you have an obscure search, you might also try a meta search engine, such as Mamma or Dogpile. These engines search numerous search engines at once.

Are all search engines the same?

No. Different search engines have identified different parts of the Web, so some pages are found in AltaVista but not HotBot, while Google might have pages that the other two have missed. Many pages are not in any search engine. Sometimes the Web page has restricted access, protected by logins and passwords that the search engine cannot bypass. Databases like Dow Jones and InfoTrac are not included in search engines for this reason.

Search engines give you results in different ways, too. If you do a search for "Microsoft", you will get hundreds of thousands of results. A search engine might give you the page that uses the word Microsoft the most as your first choice. Another might give you the page that has the most links pointed towards it as your first choice. Others might give you an advertiser's page as your first choice!

Search engines use different search techniques, just as databases do. Some want you to use Boolean operators like AND, OR, and NOT; others want you to use plus and minus signs to indicate words that must be present or absent on the page.

Read the online help for a search engine to learn the best way to use it.

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