boolean_logic

Boolean Logic and Keyword Searching

BOOLEAN LOGIC

BOOLEAN: Refers to logical or algebraic operations, formulated by George Boole; Involves variables with two values, such as Value 1 AND Value 2; Value 1 OR Value 2; and Value 1 NOT Value 2. Many databases require these connecting terms to be written in all caps in order to discern them from search terms.

AND

Vinn diagram for Boolean term AND homelessness AND children

This type of search will result in entries that must contain both words. You may use "AND" to narrow a search.

OR

Vinn diagram for Boolean term, OR infants OR babies

This type of search will result in entries that contain either of the words. Use "OR" to broaden a search.

NOT

penguin NOT Pittsburgh

This type of search will result in entries that contain the desired word but excludes entries that include both the desired and undesired term. You may use "NOT" to narrow a search, eliminating unwanted terms.

All three connecting terms can also be "nested" when more than one type of Boolean operator needs to appear in the same search statement.
Example: (rabies OR rabid) AND (skunk* OR raccoon*)

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TRUNCATION

Truncation: Use of a truncation symbol to cut off the indefinite end of a word stem --
Or a method of retrieving various forms of words sharing common roots or stems; skat* ; wom?n

Examples:

violen* will produce the following results	violence	violent	violently
preg* will produce the following results	pregnant	pregnancy	pregnancies

Truncation symbols vary for different databases.

See the list below for proper truncation symbols for some databases.

Resource	Truncation Symbol	Resource	Truncation Symbol
Library Catalog	?	CQResearcher	*
Gale	*	Factiva	$
EBSCO	*	OVID	* or $
FirstSearch	+	Project Muse	*
Internet Search Engines using Boolean Logic	*

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GLOSSARY

AND - When terms are connected by this logical operator, only those entries containing all of the connected search terms will be selected. May be used to narrow a search.

Example: homelessness AND children

BOOLEAN LOGIC - A system of connectors -- "AND," "OR," and "NOT" -- that the computer uses as instructions in carrying out a search. It is named for the English mathematician, George Boole.

ENTRY - The complete bibliographic record of information that describes the work. It usually includes author, article title, journal or periodical name, volume number, pages, and date. The term may be used inter-changeably with RECORD, POSTING, CITATION, or HIT.

FALSE HITS - Search results that do not correspond to the searcher's question. Computers locate terms that have multiple meanings, but cannot distinguish between the meanings that the user seeks and those that are not wanted.

NESTING - The use of parentheses ( ) to enclose terms to be combined with an operator when more than one type of Boolean operator appears in the same search statement.

Example: (infant* OR bab*) AND (drug* OR alcohol*) AND abuse

NOT (AND NOT, BUT NOT) - When terms are connected by this logical operator, entries that contain a particular term are excluded. May be used to narrow a search or eliminate false hits.
Example: Penguins NOT Pittsburgh

OR - When terms are connected by this logical operator, entries containing any of the connected search terms will be selected. May be used to broaden a search.

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