7. A data search method comprising: extracting a keyword to be applied to a first search process from an input question sentence; executing the first search process with using the extracted keyword; extracting answer candidates for the input question sentence based on a search result of the first search process; executing an analysis of the input question sentence, an analysis result including at least detection of a subject of the input question sentence, to generate a check expression in which (i) at least the subject of the input question sentence of the analysis result and (ii) each of the answer candidates are concatenated; executing a second search process based on the generated check expression; and selecting an output answer to the input question from among the answer candidates based on a search result of the second search process.
7. A data search method comprising: extracting a keyword to be applied to a first search process from an input question sentence; executing the first search process with using the extracted keyword; extracting answer candidates for the input question sentence based on a search result of the first search process; executing an analysis of the input question sentence, an analysis result including at least detection of a subject of the input question sentence, to generate a check expression in which (i) at least the subject of the input question sentence of the analysis result and (ii) each of the answer candidates are concatenated; executing a second search process based on the generated check expression; and selecting an output answer to the input question from among the answer candidates based on a search result of the second search process. 9. The data search method according to claim 7 , wherein the selecting of the output answer comprises: calculating number of hits corresponding to each answer candidate from the search result of the second search process; and selecting an answer candidate having the number of hits greater than a predetermined threshold value as the output answer to the input question.