17. The system according to claim 16 , wherein said dialog creating unit produces the created dialog based on (i) said received dialog having said list structure in which utterance units of said user and said agent are set as nodes and (ii) on the information on said nodes.
17. The system according to claim 16 , wherein said dialog creating unit produces the created dialog based on (i) said received dialog having said list structure in which utterance units of said user and said agent are set as nodes and (ii) on the information on said nodes. 18. The system according to claim 17 , further comprising: a dialog storage unit which stores said created dialog between said agent and said user in said branch tree structure.