Internet Search Engines

What is a Search Engine?

A search engine is a tool for finding Web pages that cover a certain topic or contain certain information.

How do Search Engines Work?

Some search engines use automated programs that ‘crawl’ across the World Wide Web, gathering information about Web pages. Other search engines are produced by companies that hire people to examine Web pages and systematically categorize them. Essentially, all types of search engines store information about Web pages and provide a means for you to type in and search on one or more keywords or phrases. The search engine then provides links to the Web pages that contain those keywords or phrases. Search engines do not evaluate Web pages, they simply link to those that contain your search terms.

Always evaluate a Web site and the information it contains before using it. See Evaluating Web Sites for more info.

Are All Search Engines the Same?

No, search engines actually vary quite a bit in their structure and capabilities. Some search engines categorize information by subject, some allow you to combine keywords with the boolean operators and, or and not.  Most search engines will allow you to search by keyword, and some even let you specify that Web pages found must contain graphical or audio components (i.e., find Web pages that contain pictures and/or digital sounds.) Some search engines cover all kinds of Web sites and Web pages, and others specialize on a certain topic, such as medicine or finding Web pages originating from a certain country. There are even search engines that search several other search engines at once; these are called Metasearch Engines. There are four main types of search engines:

• Hierarchical or Directory:  Categorize Web pages systematically in a yellow pages like structure. A human being evaluates each listed Web site for subject content and relevance. Examples of hierarchical or directory search tools include:

  Librarians' Index to the Internet  (http://www.lii.org)
  Internet Public Library (http://www.ipl.org)
  Britannica Internet Guide  (http://www.britannica.com)
  INFOMINE  (http://infomine.ucr.edu)
  Yahoo  (http://www.yahoo.com)   

• Simple Search Engines:  Allow you to type in a keyword or phrase. The crawler program automatically generated the Web sites listed. Examples of simple search engines include:

Google (http://www.google.com)
Alltheweb (http://www.alltheweb.com)
Yahoo (http://www.yahoo.com)  

• Search Engines with Advanced Searching:  Some search engines allow you to combine keywords with and, or, and not. Some offer other options for refining a search, such as limiting by date, file type and language. You can also search sites by domain, such as .edu, .com, .gov or .org. Some advanced tools will help you locate sound, image and video files as well as radio and television programs. Examples of search engines with advanced searching capabilities include:

Google (http://www.google.com/advanced_search)
Yahoo (http://www.yahoo.com/search/options)
MSN Search (http://search.msn.com/?qb=1&q=)

• Metasearch Engines:  These are tools that search two or more other search engines at once. Since no single search engine covers all existing Web pages, these are handy for covering a lot of ‘Web ground’ with one search. Keep in mind that you may lose some of the more sophisticated search techniques available in some of the advanced searches of some search engines. Examples of metasearch engines include:

  Vivisimo (http://www.vivisimo.com)
  Surfwax (http://www.surfwax.com)  

• News Search Engines:  These tools are good for searching current events. They crawl only news sites and revisit these sites several times per day. Examples of news search engines include:

  Google News (http://news.google.com)
  Alltheweb News (http://www.alltheweb.com/?cat=news)
  Daypop (http://www.daypop.com/)

Most search engines are a combination of one or even all of the above. Some allow you to do a simple search as the default, with the option of doing more advanced searching if you wish. Also, no single search engine will access all the Web pages available on the World Wide Web, so it's often a good idea to try several search engines for a more comprehensive search.

Search Engine Showdown http://www.searchengineshowdown.com/ Comparisons and reviews of search engines; Web search strategies. Search Engine Colossus http://www.searchenginecolossus.com/ Links to hundreds of search engines worldwide. Search Engine Watch http://searchenginewatch.com/ Search engine news, reviews, ratings, tutorials, and searching tips.