8. The method of claim 7 , wherein detecting the topic domain further includes: detecting a topic domain having a minimum distance among the one or more candidate topic domains having various distances.
8. The method of claim 7 , wherein detecting the topic domain further includes: detecting a topic domain having a minimum distance among the one or more candidate topic domains having various distances. 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.