The existing studies of a dialogue system can be classified into two major parts. One is a study for a practical system, and the other is a study to understand a principal of dialogue phenomena. The former focuses on robustness in practical environment for dialogue systems. However, it cannot guarantee its performance in complicated dialogue environment. The latter has studied as the plan-based model typically. It has some strong points that it can reflect complex dialogue phenomena and can infer user's intention in various situations. However, since an initial design of this model is so complicated, it is difficult for this model to be extended to effective response generation in a practical dialogue system. This paper proposes a new dialogue model using a simplified plan recognition technique and a discourse stack to effectively generate responses in a practical domain.