This work reports on the description of a specific class of clarification requests, adopted for the negotiation of pieces of information part of the common ground for argumentation strategies in human-machine interaction. Two studies are carried out to prove the adequateness of a specific form of polar question in a specific pragmatic situation, where a presupposition is contradicted by a new evidence. Whereas the first one proves the appropriateness of the negative form, the second one also demonstrate how the use of such a form, in the aforementioned pragmatic situation, can affect the principle of robustness, in terms of observability and recoverability, important in human–machine interaction applications. Given the results obtained in the two studies, dialogue systems with such capabilities are, therefore, a desirable goal, as they are expected to lead to improved usability and naturalness in conversation. For this reason, I present here a system capable of detecting conflicts and of using argumentation strategies to signal them consistently with previous observations
