The text search engine allows queries to be formed from arbitrary Boolean expressions containing the keywords AND, OR, and NOT.
information retrieval: finds documents containing 'information' and 'retrieval'
information and retrieval: same as above
information or retrieval: finds documents containing either 'information' or 'retrieval'
information not retrieval: finds documents containing 'information' but not 'retrieval'
information near retrieval: finds documents where the two words a close to each other. The rank increases as word distance decreases.