Boolean Searching on the Internet

The Basics of Boolean Logic

Excerpted from the University Libraries, University at Albany, SUNY webpage Primer on Boolean Logic

http://library.albany.edu/internet/boolean.html

March 29, 2004

“The Internet is a vast computer database. As such, its contents must be searched according to the rules of computer database searching. Much database searching is based on the principles of Boolean logic. Boolean logic refers to the logical relationship among search terms, and is named for the British-born Irish mathematician George Boole” (Primer on Boolean Logic, para 1)

Boolean logic consists of three logical operators:

OR

AND

NOT

OR logic organizes the search to retrieve all distinct records containing one term, the other, or both.

The more terms linked in an OR logic search, the more results will be displayed.

For example: University of Washington OR UW

AND logic organizes the search to retrieve all distinct records containing both terms. Records that only contain one of the terms will not be displayed.

Unlike OR searches, the more AND terms used, the fewer results will be displayed.

For example: Bush AND Iraq

NOT logic organizes the search to retrieve all distinct records containing one term as long as the other term is not present.

For example: WMD NOT Iraq

Be careful when using NOT, as it may result in your search missing useful records.

Searching the Internet with Boolean Operators

Generally, Internet search engines use Boolean logic in three ways:

1. Full Boolean logic with the use of the logical operators

2. Implied Boolean logic with keyword searching

3. Predetermined language in a user fill-in template

(Boolean Searching on the Internet, Para 1)

Full Boolean logic allows the user to simply enter the search term, say Bush AND Iraq, and the engine will conduct a Boolean search. If you want to prioritize one part of a search you may put part of it in parentheses. For example, if you wanted the terms University of Washington OR UW OR Washington State University OR WSU and you wished University of Washington OR UW to be searched for first you would enter the terms like this: (University of Washington OR UW) OR Washington State University OR WSU

Implied Boolean logic with key words allows the user to substitute spaces or symbols in place of AND, OR, and NOT. Spaces (Bush Iraq) usually translate to AND as does a + (Bush+Iraq). AND is usually the default Boolean search term. Consult the search engines help files for further information. NOT is often indicated by a – (WMD-Iraq).

Predetermined language and forms are often found on search engines for databases. Often this takes the forms of phrases like “any of these words,” “should contain the words,” or “should not contain the words” and so forth.