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The text search engine allows queries to be formed from arbitrary Boolean expressions containing the keywords AND, OR, and NOT, and grouped with parentheses. For example:

information retrieval

finds documents containing 'information' or 'retrieval'

information or retrieval

same as above

information and retrieval

finds documents containing both 'information' and 'retrieval'

information not retrieval

finds documents containing 'information' but not 'retrieval'

(information not retrieval) and WAIS

finds documents containing 'WAIS', plus 'information' but not 'retrieval'