Boolean Searching provides simple, logical rules for employing more than one word or name in a search, utilizing a strictly limited set of operators to establish the relationship between them. These operators include the words AND, OR and NOT as well as the invisible operator, which consists of placing the words together to form a PHRASE.
Consider the following sentences:
The green revolution increased crop yields in many developing countries.
Ashbel Green served in the militia during the American Revolution.
"Don’t you know they’re talkin’ ‘bout a revolution." (Tracy Chapman)
"Nature’s first green is gold" (Robert Frost)
Basic Boolean rules suggest that the first sentence could be retrieved by searching for green revolution without an intermediate word or for green AND revolution; the second sentence by green AND revolution; the third sentence by revolution or by revolution NOT green; the fourth sentence by green or by green NOT revolution.
Note that every one of the four sentences would be retrieved by searching for green OR revolution.
Note, too, that parentheses are sometimes necessary for search logic:
Paint AND external surfaces AND (oil OR latex).
Here, omitting the parentheses would permit a search to retrieve anything about latex, regardless of whether any of the other specified words appear.
Parentheses are often required when more than one operator is employed.
CAUTION! Different search engines or environments have different rules. In some (CONSULS, for example) the NOT operator is expressed as AND NOT.
More importantly, some databases, like InfoTrak, and most Web search engines have an AND or OR condition between words instead of a Phrase condition. To bring a phrase condition into play in such a case, you must use quotation marks—"Green revolution"—or make a choice between seeking any or all of the words you have selected or treating them as a phrase.
Different search engines have different way of presenting these choices. Having and exercising such choices makes for precision.
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Last Updated 08/02/01 |