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Keyword Searching

Boolean Searching

It is possible to compose complex search expressions using Boolean logic on this system. To do so, use the following terms:

AND (Boolean AND)
OR (Boolean OR)
NOT (Boolean NOT)

Boolean Operators

When used in constructing a search expression, boolean terms can be very useful in specifying exactly what information you want to find. The basis of Boolean logic can be illustrated by the following diagrams:


Boolean 'AND'

When using AND in this search expression, results retrieved will contain both blue and yellow information. The results will not include those documents containing only blue or only yellow information. In the diagram the documents retrieved by using this search expression are contained within the green area.

Example:

Genus: Acer    AND    Cultivar: Leopoldii

This search would retrieve all entries with the genus Acer which are ALSO of the Leopoldii cultivar. However, it would not retrieve other entries of the genus Acer.


Boolean 'OR'

When using OR in this search expression, results retrieved will contain either blue information, or yellow information, or blue and yellow information together. Such a search will not merely retrieve documents containing only blue information or only yellow information. In the diagram the documents retrieved by using this search expression are contained within all the colour areas. OR is an inclusive operator and provides the broadest search results.

Example:

Genus: Acer    OR    Cultivar: Leopoldii

This search would retrieve all entries with the genus Acer and all entries of the Leopoldii cultivar. In this case, all entries of the genus Acer would be retrieved, along with those which happened to be of the Leopoldii cultivar.


Boolean 'NOT'

When using NOT in this search expression, results will contain only blue. The NOT operator will exclude yellow completely and thus any green information will be excluded also. It is important, therefore, to be careful when using this operator in order to avoid hindering your search. In this diagram the documents retrieved by using this search expression are contained within the blue area. NOT is an exclusive operator and can narrow search results quickly if used precisely.

Example:

Genus: Acer    NOT    Cultivar: Leopoldii

This search would retrieve all entries with the genus Acer but NOT of the Leopoldii cultivar. In this case, all entries of the genus Acer would be retrieved, EXCEPT those which were of the Leopoldii cultivar.

* This document adapted from http://adam.ac.uk/info/boolean.html.

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