Search Engines Search Engines June 20 2005 LIBS100 Linda Galloway LIBS

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Search Engines Search Engines June 20 2005 LIBS100 Linda Galloway LIBS Powered By Docstoc
					Search Engines

 June 20, 2005
 Linda Galloway
 LIBS 100 Word of the Day

A search engine that queries
   other search engines and
  then combines the results.
 What is a search engine??
A program that searches documents for
 specified keywords and returns a list of
   the documents where the keywords
              were found.
   How Search Engines Work
• Spider or crawler
  – Visits page
  – Follows links on page to other pages
  – Sends terms to the holding area
• Index
  – Sorts through holding area
  – Stores significant words with a link to pages that have those
  – Ignores words like “the” “and” “of” “to”
• Search engine software
  – Accepts your query term
  – Finds matching pages
        Boolean Operators
• AND (+) locates records containing
  both terms.
• OR locates records containing either
• NOT (–) locates records containing first
  term, but not the second
• Most of the time, operators MUST be
     Major Search Engines
         Top Choices
             Crawler Based
• Google

• Yahoo

• Ask Jeeves
             (results from Teoma)
          Major Search Engines
             Good Choices
             Crawler Based
• AlltheWeb
(editorial results from Yahoo)
• AOL Search
(editorial results from Google)
• Hotbot
(editorial results from Yahoo, Google,
• Teoma
        Subject Directories
• Human-powered
• Humans review, select, categorize web
• Changes to a site will not affect its
  listing on a directory
How Subject Directories Work
• Humans decide on a set of categories
• Humans review web sites (sometimes
  based on suggestions from users)
• Humans assign a site to a category
• Sometimes humans write actual content
    Subject Directories Ranking
•   No automated ranking algorithm
•   Humans put categories in order
•   Sites usually listed alphabetically
•   Sponsored links
          Yahoo Directory
• “Classic” Yahoo – uses humans to
  organize web sites into categories
  – Yahoo directory only directory based
    search engine to get top rating
• Librarians Index to the Internet
Subject Directories – Pros and
• Pros
  – Human review/intervention
  – Sites are organized by topic
  – Sites can’t artificially inflate their ranking
• Cons
  – Very limited content
  – Only updated when humans find time
  Popular Subject Directories
• Yahoo Directories
• (
• Librarian’s Index to the Internet
• Google Directories
• Infomine
• LookSmart (
       So Which Do I Use?
• Search engine
  – You already have a very specific topic
  – You have a very new topic/need very latest
  – You need quick facts
• Subject directory
  – You have a broad topic and want to narrow
    it down
  – You aren’t sure how to get more specific
       Metasearch Engines
• A search engine that queries other
  search engines and then combines the
  results that are received from all.

• Searcher uses a combination of search
  engines at one time.
       Metasearch Engines

• User cannot tailor search to each search

• Dependant on other search engines’
   Good Metasearch Engines
• Dogpile
• Vivisimo
• Hotbot
• Kartoo
• Mamma
          Editorial Results
         (or Main Results)
Results that are gathered by crawling or
 indexing web sites.

Web masters pay a lot of attention to
 how their sites are listed.

These are non-fee based listings
             Paid Listings
Web sites pay a fee to be among top hits
 for certain keywords.

With some search engines, it is difficult to
 tell difference between editorial and
 paid listings.

Paid hits are probably not the most
Search Engines

Results Listing

• Rothenberger, Michelle. “Search Engines.” 6 Feb 2005

• Staff. “Resources, INFS100.” Minneapolis Community
  and Technical College. 6 Feb 2005

• Sullivan, Danny. “Search Features Chart.” 26 Oct 2001. 6 Feb 2005
           Assignment 3

           Due June 22, 2005

• Handed out in class on Wednesday,
  June 15th

• You will perform a focused search using
  two search engines on your research
               Assignment 3
•   Must Document Your Sources!!!
•   Use MLA format
•   Described on your Assignment
•   Follows this format for web pages:
Author’s Last Name, Authors First Name. “Title of Web
  Page.” Title of Complete Web Site, if Applicable. Date
  of Publication or last revision. Date accessed <Web
  Page Address (or URL)>.
             Like This!
Sherman, Chris. “Metacrawlers and
  Metasearch Engines.” 15 March
  2004. 8 Feb 2005

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