In Multi-Agent Systems, a dialogue represents a coherent sequence of agent messages which bear upon the same subject [1]. In this paper we discuss a flexible and dynamic approach to formalize agent dialogues. Our approach does not require agents to follow a fixed start-to-end sequence of messages in a dialogue to achieve their goals. Instead dialogues are constructed dynamically and progressively based on individual message exchanges. The individual message exchanges are governed by dialogue rules or syntax formats. This modular approach towards dialogue composition allows agents to perform flexible actions and adapt their behaviour according to the changes in the system