41. A computer implemented method of providing a natural language answer to a natural language question, the method comprising: receiving, over a computer network, a query comprising a grammatical question; submitting the query to a lookup engine; receiving initial search results from the lookup engine, the initial search results comprising a plurality of documents, wherein the initial search results comprise a ranking of the plurality of documents according to relevance; identifying, in the plurality of documents, a plurality of candidate sentences; calculating, for each candidate sentence, a measure of commonality between the candidate sentence and the query; assigning, to each candidate sentence, a score, wherein the score comprises (1) a rank of the candidate sentence according to the ranking of the plurality of documents, and (2) the measure of commonality between the candidate sentence and the query; sorting the candidate sentences according to score, whereby a rating of candidate sentences is produced; and sending, over a computer network, a reply to the query, the reply comprising at least a top candidate sentence from the rating of candidate sentences.
41. A computer implemented method of providing a natural language answer to a natural language question, the method comprising: receiving, over a computer network, a query comprising a grammatical question; submitting the query to a lookup engine; receiving initial search results from the lookup engine, the initial search results comprising a plurality of documents, wherein the initial search results comprise a ranking of the plurality of documents according to relevance; identifying, in the plurality of documents, a plurality of candidate sentences; calculating, for each candidate sentence, a measure of commonality between the candidate sentence and the query; assigning, to each candidate sentence, a score, wherein the score comprises (1) a rank of the candidate sentence according to the ranking of the plurality of documents, and (2) the measure of commonality between the candidate sentence and the query; sorting the candidate sentences according to score, whereby a rating of candidate sentences is produced; and sending, over a computer network, a reply to the query, the reply comprising at least a top candidate sentence from the rating of candidate sentences. 47. The method of claim 41 , wherein each score comprises a geometric mean of (1) the rank of the candidate sentence according to the ranking of the plurality of documents, and (2) the measure of commonality between the candidate sentence and the query.