9. The method of claim 8 , wherein the calculating the distance involves using the history information relative to the previous dialogue for the output text obtained as the result of the backward decoding of the previous dialogue and information obtained from a probability factor database having probability factors used for calculating the distance for each of the one or more candidate topic domains.
9. The method of claim 8 , wherein the calculating the distance involves using the history information relative to the previous dialogue for the output text obtained as the result of the backward decoding of the previous dialogue and information obtained from a probability factor database having probability factors used for calculating the distance for each of the one or more candidate topic domains. 12. The method of claim 9 , wherein performing the backward decoding comprises performing a backward sub-decoding with reference to the global language model database, if the text is not output even though the backward decoding has been performed with reference to the specific topic domain language model database.