Using and Evaluating Electronic Resources
Lesson 4

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Boolean Operators and Truncation Searching

Online databases, indexes, catalogs, and the World Wide Web contain vast quantities of information. In order to tap into their full potential, you must become proficient at constructing searches.

Believe it or not, computers cannot think. Computers cannot interpret your intent when you type in words. However, a computer will do exactly what you tell it to do when you type in a search. To the computer, your combination of words is nothing more than a collection of characters. It tries to match your exact terms in the exact order you typed them. Most failed searches are the result of poorly constructed search queries.

How you combine terms and concepts has a direct bearing on what you retrieve.This lesson will teach you the basic tools, strategies, and techniques for finding your information "needle" in the "information haystack."

Boolean Operators

Boolean operators are words used to make a logical search query.
They enable you to broaden or narrow your search. Your research questions, your thesis, must be organized into a form that a computer can manipulate.

Boolean operators help bridge the gap between human thought and language and computers which use mathematical logic to compute--not think. You may have already encountered their "inventor," George Boole, in your Introduction to Logic course.

A skillful searcher can combine Boolean operators and knowledge of database fields to articulate a search that causes a computer to retrieve relevant results from a database. A skillful searcher can also analyze the reasons for failed searches and make intelligent adjustments

Online searching is an art. Take heart! Even the most advanced, experienced searchers rarely get it right on the first try. Be prepared to adjust--with intelligence.

The basic Boolean operators AND, OR, NOT.

Boolean "AND"

The Boolean AND narrows your search by retrieveing only documents that contain every one of the words you enter. The more you enter, the narrower your search becomes.

EXAMPLE: truth AND justice
EXAMPLE: truth AND justice AND ethics AND congress

Boolean "OR"

The Boolean OR expands your search by returning documents in which either or both words appear. Since the OR operator is usually used for synonyms, the more words you enter, the more documents you will retrieve.

EXAMPLE: (college OR university)
EXAMPLE: (college OR university OR campus OR higher education)

* when using the OR operator, you must use a parenthesis to group your terms

Boolean "NOT"

The Boolean NOT limits your search by returning only your first word but not the second.

EXAMPLE: bulimia NOT anorexia

Translating Questions into Computer Searches

Step 1: State your thesis in the form of a researchable question

EXAMPLE: What are the effects of television violence on young adults?

Step 2:
Pull out the key words and concepts from your question

EXAMPLE: television   violence   young adults

Step 3:
Create a list of synonyms

EXAMPLE: television   TV   movies  cartoons  news

EXAMPLE: violence  guns  murder  rape  gangs  war

EXAMPLE: young adults  teenagers  adolescents  teens  youth

Step 4:
Use Boolean operators to connect groups of concepts

(television OR TV OR cartoons OR news) AND (violence OR guns OR murder) AND (teenagers OR youth OR adolescents)

Your Turn

Using the four steps demonstrated above, translate one of these thesis questions into a computer search.

"What were the political advantages of Constantine's conversion to Christianity."

"What are the scientific and ethical issues of reproduction research, specifically those related to cloning?"

Boolean logic is not always simple

Databases may handle Boolean operators differently.

  • Some require the operators to type in capital letters while    others do not.
  • Some use drop-down menu options to spell out the Boolean    logic in short phrases.
  • Some use (+ ) and (-) symbols in place of AND and NOT.
  • Some search multiple word combinations as exact phrases,    others as separate words.

Many databases have online help you can read to learn how Boolean operators are used.

Truncation Searching

In addition to Boolean searching, truncation provides us with additional flexibility in searching. Remember we said earlier that computers are literal. They will not find 'bulimic' if you type 'bulimia.' Computers will not find 'violence' if you type 'violent.'

Truncation allows the computer to search for multiple forms of a word. The generally accepted symbol for truncation in Spring Hill College Library online databases is an asterix (*). The Spring Hill College Library online catalog uses ($) for truncation.



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