go to


KEYWORDS AND BOOLEAN OPERATORS (continued)

boolean operators
When searching a database or search engine, keywords should be combined using Boolean Operators. The three basic Boolean Operators are the terms AND, OR, and NOT. Boolean searching is based on a system of symbolic logic developed by George Boole, a 19th century English mathematician. Most computer databases and Internet search engines support Boolean searches. Boolean search techniques result in accurate results. The power of Boolean searching is based on combinations of your keywords connected by Boolean operators. In our last example, you would execute your search by entering breaders and "standard poodles" and Florida.

To further illustrate the use of Boolean Operators, look at these diagrams:



The examples above illustrate general topics expressed with just two keywords. Actual search strings which express complex topic ideas may consist of several keywords and combinations of Boolean operators. For example, the topic statement "Automobile air bags are not safe for children" might result in the search string:

automobiles AND "air bags" AND children AND safety

Most databases and search engines support complex Boolean searches. If you have a complex search using more than one operator, you can nest your search terms. Search terms and operators included in parentheses will be searched for first, then terms and operators outside the parentheses. A search for:

(ADD OR attention deficit disorder) AND college students

will search for documents containing either the acronym ADD or the phrase attention deficit disorder first, then narrow the search results only to those documents which also contain the words college students.

Here is an example that illustrates how you can use keywords and Boolean operators to get better results.

If your chosen topic area is television violence, you may find this too broad an area to cover. As you do research, you may find most of the sources discuss television violence and children. You could narrow this further to the question, "What is the effect of television violence on children?"

Keywords for this might include: television violence and children. Other terms might include: teenagers, media, or aggression.

To refine or narrow your search, use AND:

children AND "television violence"

(Using the phrase "television violence" requires all documents retrieved to contain that exact phrase. If a document refers to "violence on television" but never uses the phrase "television violence", that document will not appear in the list of results. Phrases are extremely useful, just use them wisely.)

To broaden your search to include a wider range of age groups, use OR:

(children OR teenagers) AND "television violence"

If your search results include areas you are not interested in, like cartoon violence, you can eliminate terms with NOT:

children AND "television violence" NOT cartoons

>> continue