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Search Tips

The site search uses free-form full-text technology, yet it also understands Boolean syntax as well, for more experienced searchers.

Operator Usage Comments
SPACE apple banana Read as 'apple AND banana'.
AND apple AND banana Upper case is operator, Lower case is ignored
& apple & banana The & character is read as 'AND'
OR apple OR banana Upper case is operator, Lower case is ignored
| apple | banana The | character is read as 'OR'
NOT apple AND NOT banana Upper case is operator, Lower case is ignored
~ apple & ~ banana '& ~' is read as 'AND NOT'
XOR apple XOR banana XOR is read as 'exclusive or'
^ apple ^ banana The ^ character is read as XOR

Example searches

You can type a question as you would pose the question verbally.
How do I prepare my taxes
[ Common words (how, do, I, and my) are ignored. The resultant query would be 'prepare AND taxes' ]

Or you could just type in a keyword query.
apple banana
[ The resultant query would be 'apple AND banana'
(AND is the default operator) ]

Or, you could type in a Boolean query.
apple OR ( banana AND NOT jello XOR ( spam OR ham ) )
[ The search engine recognizes AND, OR, NOT, XOR and nested parenthesis ]

We also have a shorthand Boolean syntax.
apple | ( banana & ~ jello ^ ( spam | ham ) )
[ This means the same as the preceding query ]

Stemming

Search queries should use the root stems of search terms. For example, if you seach for 'preparation', A search for 'prepar' and will find occurances of: prepare, prepares, prepared, preparing, and preparation.

Case, punctuation and other things

Search queries ignore CASE. So searching for Cherries, cherries, or CHERRIES, would all give the same results.
Punctuation characters are ignored, as are extraneous whitespace characters.

Ranking (Sort order)

A number of criteria are used to determine ranking. If the search term is an 'Important' word in the document, the document will appear higher in the list. Importance is determined by the following:
bulletword frequency
If the search term is used in the document frequently.
bulletword CASE
If the word is capitalized in the document
bulletword in Title
If the word appears in the document Title
 

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Gordon.D.Holman@nasa.gov

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This site last updated November 10, 2008.