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Using Boolean logic in your search

Using Boolean logic in your search

Boolean searching is based on a system of symbolic logic developed by mathematician George Boole. Most  periodical databases support Boolean searches. Boolean search techniques may be used to perform accurate searches without producing many irrelevant documents.

When you perform a Boolean search, you search the computer database for the keywords that best describe your topic. The power of Boolean searching is based on combinations of keywords with connecting terms called operators. The three basic operators are the terms "and", "or' and "not".

AND
The operator "and" narrows a search by requiring results to contain contains both of the terms specified.

The diagram above illustrates the AND search. The left circle includes all records including the term 1. The right circle includes all records including the word term 2. When the computer searches its database and retrieves every record containing both of the words term 1 and term 2, only the records from the intersecting, green shaded area will be retrieved.

Several keywords may be used to narrow searches with the AND operator.

OR
The OR operator broadens or widens a search to include documents containing either keyword. The OR search is particularly useful when there are several common synonyms for a concept or variant spellings of a word.

As the diagram shows, the computer searches for all documents containing term 1 (left circle) and all documents containing term 2 (right circle). All documents represented by both circles will be retrieved. OR searches often produce large numbers of documents.

NOT
Combining search terms with the NOT operator narrows a search by excluding unwanted terms.

The diagram illustrates the search by retrieving documents including term 1 (left circle) and excluding documents with the term 2 (right circle). Retrieved documents are shown in the green shaded area.

Boolean search terms may be combined in various ways to carefully refine searches.

Last modified: 1/8/2004 4:03 PM by by M. Potter

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