24. A method of operating a computerized information retrieval system where information is retrieved from a database containing documents in response to user queries, the method comprising: receiving a natural language query specifying information to be retrieved; extracting terms that appear in the query; detecting words that indicate negation of interest in certain information; if a word that indicates negation is detected, determining which of the terms belong to a negative portion of the query and which of the terms belong to a positive portion of the query; generating an alternative representation of the query that includes the terms in both the positive and negative portions of the query; matching the alternative representation of the query against the database by determining a measure of relevance for each document; providing a set of documents that satisfy a retrieval criterion; and within the set of documents, so provided, segregating those documents that satisfy only the positive portion of the query from those documents that satisfy both the positive and negative portions of the query.
24. A method of operating a computerized information retrieval system where information is retrieved from a database containing documents in response to user queries, the method comprising: receiving a natural language query specifying information to be retrieved; extracting terms that appear in the query; detecting words that indicate negation of interest in certain information; if a word that indicates negation is detected, determining which of the terms belong to a negative portion of the query and which of the terms belong to a positive portion of the query; generating an alternative representation of the query that includes the terms in both the positive and negative portions of the query; matching the alternative representation of the query against the database by determining a measure of relevance for each document; providing a set of documents that satisfy a retrieval criterion; and within the set of documents, so provided, segregating those documents that satisfy only the positive portion of the query from those documents that satisfy both the positive and negative portions of the query. 25. The method of claim 24 wherein: the alternative representation of the query includes a plurality of individual representations; said step of determining a measure of relevance for each document includes, for each document, determining a score for each of the individual representations, and combining the scores; and at least one of the individual representations does not include the terms in the negative portion of the query.