Boolean Operators

Objective: Students will understand Boolean operators and how they

function when searching for information.

Boolean logic

• Boolean logic is named for mathematician George Boole who defined the system of logical operations.

• Boolean operators are often used when searching article databases, library catalogs, and search engines. The operators show a relationship between keywords in a search.

Image taken from http://www.encyclopedia.com/topic/George_Boole.aspx

The three Boolean operators are:ANDOR

NOT

Boolean operators are used to expand or limit the number of results in a search.

Diagrams visually explain how Boolean operators work.

Use Boolean operators to connect and search for the keywords found in your research question.

For example, SIRS Knowledge Source uses them to perform advanced searches.

Google’s Advanced Search also uses Boolean operators.

AND narrows your search.Use AND when you want your results

to include all terms .

Only records with both terms will be found (the purple area).

OR broadens your search. Use OR when searching synonyms and closely related

keywords. OR will find results with one term or the other or both (the entire green area).

ACT SAT

NOT narrows your search. Use NOT when you want to exclude a keyword from your search. Cheating NOT Test will find results with

the word Cheating, but will exclude any results with the word Test.

TestCheating

Only records with the word cheating that do not include the word test will be found (the green area).

You can also combine Boolean operators

For example: Cheating AND (ACT OR SAT)

This search would find results containing either ACT or SAT or both words (the red & purple areas) AND those areas that overlap with cheating (the purple area). So this search expands your search to include both tests and then limits the results to include just those articles that contain the word cheating.

SAT

Cheating ACT

Boolean operators are an effective tool when searching article databases, library

catalogs, and search engines.AND narrows your searchOR broadens your searchNOT narrows your search

Summing Up