Appendix 2 - Boolean Search Operators
All online catalogues and article indexes use Boolean operators to combine
keywords and search concepts in their search commands. The three basic
Boolean operators are AND, OR, and NOT.
AND - When you combine your keywords with the Boolean operator AND, you
are narrowing your search to those records that contain each keyword you have
chosen. For example, you may want to structure a search like:
stress
and health
When you do a search for the keyword "stress" alone,
there may be 256 citations in the resulting set. Similarly, when you
search for the keyword "health" the database provides 785
citations. However, when you combine them as one search using the AND
Boolean operator, as in the search for "stress and health," you find
that the database provides only 72 citations, each of which will include both
keywords.
Pictorially, you will get
only those results coloured in green below:
OR - The OR operator broadens your search by letting you search for
alternate terms, synonyms and related concepts. A sample search might be
"stress or fatigue." You will get additional results, in fact,
everything coloured green in the illustration below.
NOT - This operator is very useful in eliminating records which have
an unwanted keyword in them. It narrows your search by exclusion. For example, you might want to use it when researching the effects of stress in
order to eliminate metal fatigue records which pop up as in: stress not
metal.
Be careful when using this operator as it can also take out desirable
records unintentionally. It is often best to work with the AND operator
instead. Ask the reference librarian for assistance when using NOT.
Return to top screen.
XOR - Unique to MARLIN is the XOR operator. The definition of
this is that either one or the other keyword may be present in any record, but
not both. Even the librarians have had difficulty understanding when one
might use this operator, but it is easier to draw than to explain!
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