Patent ID: 7587389

Claim:
A question answering system comprising: a CPU; a question input unit that inputs a question; a search unit that executes search processing based on the input question; an anaphoric analysis unit that executes anaphoric analysis processing on a search result of the search unit; an information extraction unit that extracts sentences, which include expressions having a reference relation therebetween, as reference relation sentences, the reference relation determined by finding an anaphoric relation between a first expression and a second expression of at least one of a noun phrase, a pronoun, and a zero pronoun between respective sentences in the search result based on a result of the anaphoric analysis executed by the anaphoric analysis unit, wherein the information extraction unit selects a first candidate sentence containing the first expression from a passage obtained as the search result, and selects a second candidate sentence containing the second expression, which is a reference relation sentence of the first candidate sentence; and the information extraction unit selects as the first candidate sentence from the passage obtained as the search result, a sentence containing more words corresponding to a search keyword used by the search unit and another sentence adjacent thereto; and if a reference relation sentence of the selected first candidate sentence is present, the information extraction unit selects the reference relation sentence of the selected first candidate sentence as the second candidate sentence; and an answer candidate extraction unit that extracts an answer candidate from the first and second candidate sentences selected by the information extraction unit.