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
  also finds documents containing 'information' or 'retrieval'
• information and retrieval
  finds documents containing both 'information' and 'retrieval'
• information not retrieval
  finds documents containing 'information' but not 'retrieval'
• (information not retrieval) and web
  finds documents containing 'web', plus 'information' but not 'retrieval'
• information*
  finds documents containing words starting with 'information'