12. The method according to claim 8 , wherein the extracting the feature values further extracts, as each of the feature values, a surface expression of a string.
12. The method according to claim 8 , wherein the extracting the feature values further extracts, as each of the feature values, a surface expression of a string. 13. The method according to claim 12 , wherein the extracting the feature values calculates an appearance frequency of the surface expression of the first difference string as a degree of importance, and wherein the presenting the correction candidates is in order of decreasing the degree of importance.