Lesson 7 Contents:

Learning Objectives

I. A Brief Review of Basic Keyword Searching

II. Boolean Logic: The use of OR and AND

III. Advanced Keyword Searching

IV. Key Points to Remember

Lesson Seven Quiz

Lesson Seven Exercise

II. BOOLEAN LOGIC: The Use of OR and AND

Advanced keyword searching is based on a method of combining search terms known as Boolean logic. Named after George Boole, a 19th century British mathematician, Boolean logic allows you to use logical operators (sometimes called Boolean operators) to combine keywords. The 2 most common logical operators are OR and AND. Let’s examine each.

OR – instructs the computer to retrieve records containing any one or more of your search terms. Most commonly used to link together synonymous terms as a way to broaden your search.

For example, if you were looking for articles about college, you might decide that articles containing the synonymous term “university” might also be relevant. Therefore, you create the search statement “college OR university.” You are asking to see any article containing either the word “college,” OR the word “university,” OR both words. This search statement can be diagrammed as follows:

OR

COLLEGE OR UNIVERSITY

* The 1st shaded circle represents all the records containing the word “college.”

* The 2nd shaded circle represents all the records containing the word “university.”

* The shaded overlap represents the records containing both words.

Using the InfoTrac OneFile, here’s how the search translates into number of articles retrieved:

If you add more synonymous terms to your search statement, you will retrieve more records. (A simple rule to remember is “OR is MORE.”) Consider, for example, adding the term “campus” to your search statement:

COLLEGE OR UNIVERSITY OR CAMPUS

With the addition of the 3rd search term, your search results increase significantly:

AND – instructs the computer to retrieve records that contain all of your search terms.

For example, you’re interested in articles that discuss the connections between crime and poverty. Therefore, you enter the search statement: “crime AND poverty,” which can be diagrammed as follows:

AND

POVERTY AND CRIME

* Records will be retrieved only if they contain BOTH the word “poverty” AND the word “crime,” as indicated by the shaded area.

* Notice that you do not retrieve records that contain only the word “poverty,” or only the word “crime.”

Again using the InfoTrac OneFile, here are the search results. Notice how combining terms with AND dramatically reduces the final number of hits, since both words must be present in the records retrieved.

If you add an additional term, your search results will be reduced even further. For example, let’s add the term “gender”:

POVERTY AND CRIME AND GENDER

Your search results are now as follows:

To summarize:

OR means “I want to see records that contain any one or more of the terms I enter. I don’t care which.” The use of OR will increase your search results.

AND means “I want to see records that contain all of the terms I enter. They all must be there somewhere in the record.” The use of AND will decrease your search results.