Conversations occurring in a society of communicating systems can be studied according to a model where the main concept is a theory and exchanges are governed by syntactic, semantic, and pragmatic devices. In the present paper we discuss these issues, focusing on the role played by situations where context marks are meaningful for governing dialogues. We take the case of intelligent tutors, in particular one for logic programming under development, as the application example behind this research. Finally, we stress that the flexibility of interactions depends to a great extent on the ability of knowledge-based systems to face open situations.