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Health On the Net Foundation's 
Medical Document Finder
Medhunt Help - Boolean operators

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MedHunt allows Bolean searches, whereby add the words and, or in your searches or adjoin its, as in Breast and Cancer, Breast or Cancer, and "Breast Cancer". These powerful commands create a relationships between words of your query and help to refine it.
- The use of Boolean operators is significant only with more than one word in your search.
- To use these Boolean commands you have to check the corresponding box.
- No check of Boolean operators box will imply the use of the default selection: and
Example with the query breast cancer:
And  Default selection  
Add and in your searches as in breast and cancer  
Return only sites with all words you type in the form. 
The result will include all the pages containing the both words breast and cancer
Or  Add or in your searches as in breast or cancer  
Return sites with each words of your  request. 
The result will include all the pages with the word breast and all the pages with the word cancer
Adj  Adjoin your searches as in "breast cancer 
search for all your words as nearby words. 
the result will include all the sites with breast cancer as it is. 
Results - Hit list

For the given search terms it is abvious that the lenght of the hit list depends of the type of Boolean operator box you checked.
A search with or will yield a list of sites much longer than with and which will give at its turn a list of sites much longer than with the use of the adjacent operator.

A graphical interpretation will help you to better understand these powerful concepts.
Relevancy of the query

Example:you are looking for information about the Breast Cancer,
The choice to adjoin the words as in "Breast Cancer", that is to use the adjacent operator, is much more appropriate than to use and or or. Because you are not interested for information about cancer only or breast only but you want to find paragraphs dealing with breast cancer.

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  http://www.hon.ch/MedHunt/Help/Boolean.html Last modified: Tue Nov 24 1998