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• Boolean Logic
• Truncation
• Phrase Searching
theTHEORY
• Boolean logic allows users to combine search terms.
• Boolean logic allows users to both expand or limit their search.
Boolean Logic
• This is achieved by using Boolean operators AND, OR and NOT (always in caps), to link the search terms in searches.
• Boolean logic is used in many computer applications including search engines, web directories, databases and some CD ROMS.
Boolean Logicthe
THEORY
• An example will explain how the operators (or link words) work to limit or expand your search.
• The question for this search is:
How are students affected by computers?
Boolean LogictheTHEORY
• First it is necessary to isolate the major words from the question to use as search terms.
• These terms are referred to as keywords.
E.g. The keywords from this example are STUDENTS and COMPUTERS.
Boolean LogictheTHEORY
• The first operator (or link word) to investigate is OR.
• How will it affect the search on students and computers?
• Will the search expand or will OR limit the search?
theTHEORY
Boolean Logic
When you use the OR operator in“students OR computers”
the documents retrieved have either of the keywords in them.
UsingOR
ORhighest
retrieval
students & computers
Boolean Logic
• The second operator (or link word) to investigate is NOT.
• How will it affect the search on STUDENTS and COMPUTERS?
UsingNOT
Boolean Logic
When you use the NOT operator in“students NOT computers”
the items retrieved refer to students only.
UsingNOT
students
NOTPages contain
one but notthe other term
Boolean Logic
• The third operator (or link word) to investigate is AND.
• How will it affect the search onSTUDENTS and COMPUTERS?
UsingAND
Boolean Logic
When you use the AND operator in“students AND computers”
only items containing references to both students and computers are retrieved.
UsingAND
students & computers
ANDnarrows the
search
Boolean Logic
• Some search engines have additional boxes or links which allow you to further narrow the results of your search.
• Google has a search within results link at the bottom of their results page.
E.g. - search students AND computers- click on search within results
- type in effects and press enter
Try this: http://www.google.com/
Boolean LogicGOOGLETIP
• Some search engines and databases require users to click on Advanced Search to use Boolean searching.
• Individual engines and directories use different Boolean operators.
• The examples of how different engines use Boolean logic will explain this further.
SearchHINTS
Boolean Logic
• the + (plus) symbol is used instead of AND. Place immediately before all terms to be included in the search. E.g. +animals +endangered
• the - (minus) symbol is used instead of NOT. Place immediately before all terms to be excluded. E.g. +animals –mammals
• the OR is not available.
Boolean Logic – Basic SearchUsing
DirectHit
Try it : http://www.directhit.com/
With Boolean searching on DirectHit:
• the AND is implied. Type in all terms to be included in the search. E.g. animals endangered
• the - (minus) symbol is used instead of NOT. Place immediately before all terms to be excluded. E.g. animals –mammals
• the OR operator (in capitals) is placed between terms.
E.g. astronomy OR planets
Boolean Logic – Basic SearchUsing
Try it : http://www.google.com/
With Boolean searching on Google:
• + (plus) is used instead of AND. Place immediately before all terms to be included in the search.
E.g. +animals +endangered
• - (minus) is used instead of NOT. Place immediately before all terms to be excluded.
E.g. +animals –mammals
• () (parentheses) are used instead of OR. Place all terms in parentheses.
E.g. (astronomy planets)
Boolean Logic – Basic SearchUsing
AllTheWeb
Try it : http://www.alltheweb.com/
With Boolean searching on AllTheWeb:
• Truncation is a tool which can broaden a search.
• Users enter part of a word in order to ensure retrieval of all documents containing variations of the word.
• Not all search engines allow truncation.• Try the next example using Yahoo.
TruncationSearchHINTS
Tool to broaden searches:
1.Right hand truncation with*•Type sight*•You will retrieve documents with sights, sightseeing, sighted etc.
UsingYAHOO
Try it : http://www.yahoo.com/
Truncation
2. Internal “wild-card” truncation with *
• Type colo*r
• You will retrieve documents containing both colour and color.
UsingIXQUICK
Try it : http://www.ixquick.com/
Truncation
• Phrase searching offers another tool which will contribute to a successful search on the Internet.
• Try the following examples:
Phrase SearchingSEARCHHINTS
• Enclose terms to be searched as a phrase in quotes
“The Gettysburg Address”
“The Battle of Trenton”
• The phrase will be retrieved exactly as keyed in.
Try it: http://www.google.com/
Phrase SearchingUsingGOOGLE
Works Cited
Henninger, M. Don’t Just Surf. Effective Research Strategies for the Net. Sydney: U of New South Wales, 1999.
Barlow, Linda. “How Search Engines Work.” The Spider’s Apprentice: A Helpful Guide to Web Search Engines.” 22 Sept. 2001. Monash Information Services. 4 Oct. 2001 <http://www. monash.com/spidap4.html>.
Tyner, Ross. “Internet Search Tools and Techniques.” Electronic Information Literacy: Library and Internet Research. 25 Aug. 2000. Okanagan U Coll. 4 Oct. 2001 <http://www.ouc.bc.ca/ library/eil/research/internet3.html>.
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