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How Search Engines Work
By Danny Sullivan, Editor (October 14, 2002)
The term "search engine" is often used
generically to describe both
  • crawler-based search engines and,
  • human-powered directories.
    Today, it extremely common for both types of
    results to be presented in a search engines called
  • "Hybrid Search Engines"
  • 
    Crawler-Based Search Engines
    
  • such as Google (http://www.google.com)
  • create their listings automatically
  • they "crawl" or "spider" the web
  • changing your web pages can affect how you are listed [top]
  • 
    Human-Powered Directories
    
  • such as the Open Directory (http://www.dmoz.com)
  • depends on humans for its listings
  • You submit a short "description", or editors write one for sites they review
  • search matches only the descriptions
  • changing your web pages has no effect
  • site with good content might be more likely to get reviewed than a poor site [top]
  • 
    Hybrid Search Engines
    
  • Usually, a hybrid search engine will favor one type of listings over another
  • such as MSN Search is more likely to present human-powered listings from LookSmart. However, it does also present crawler-based results (as provided by Inktomi).

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