Boolean Operators & Truncation [Olympic College]

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Boolean Operators and Truncation

by Library Faculty (rev. May 2001)

Use Boolean operators to search for information in databases such as library catalogs, periodical indexes, and search engines on the Internet. They add precision and flexibility to searching. Boolean operators include AND, OR, and NOT. The use of Boolean logic often allows you to retrieve a high number of relevant materials.

The word AND narrows a search. All concepts connected with AND must be present in order for items to be retrieved.
The word OR expands a search. Use OR to gather synonyms. Surround synonyms with parentheses.
The word NOT excludes concepts or meanings. Use NOT with extreme caution.

AND

This diagram represents a search for materials on the topic "the effects of television violence on childrenî. Each circle represents the body of information containing each particular term. The shaded area in the center represents the intersection of all three terms when they are joined by a Boolean AND. The shaded area also represents the body of information you would retrieve with this search statement. By using AND you are telling the computer to retrieve only items that contain all three words.

There are some differences in the way AND is expressed in different databases.

Some common practices are:

use a plus sign to require terms. + children + media + violence
use a pull-down menu to specify ìall of theseî or 'must contain'
do nothing when AND is the default operator, that is, AND is the assumed connector between terms.

Children AND Television AND Violence

Here is a search for materials on either the topic ìCity Planningî, or ìUrban Planningî. Notice how the OR operator gathers the two synonymous terms, ìcityî and ìurbanî, together. By using these terms connected by OR in your search, all records containing one term, the other, or both will be retrieved. The shaded area represents the retrieval of materials containing ìcityî OR ìurbanî, but must also include the term ìplanningî, which is joined with AND.

Like the AND operator, OR, can look a little different as you move from database to database.

Sometimes, instead of OR, you:

use a pull down menu to select "any of these" or "can contain", or,
do nothing because OR is the assumed operator

(City OR Urban) AND Planning

NOT

Your search for materials on the topic ìdolphin behaviourî brings you lots of materials about the Miami Dolphins football team. By specifying NOT ìfootballî, you can exclude irrelevant material. The shaded area shows what you retrieve using the NOT command.

Dolphins AND Behavior NOT Football

Truncation and Wildcards

Truncation and Wildcards are useful tools for searching for words that have a variety of possible spellings and endings. Depending upon the database or search engine you use, a symbol, such as a " * " or " ? ", is normally used as either the truncation or wildcard character. Consult the ìHelpî file of the database or search engine to determine the appropriate truncation or wildcard symbol.

Examples:

Truncation

child?

gets:

child, child ren , child bearing , child birth , child hood , child ish ,

child less , child 's Ö.

Wildcard

wom*n

educat**

gets:

wom e n, wom a n, wom y n

educat or , educat ed but not ìeducationî because this wildcard requires two letters.

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