This article aims to provide foundations for a new approach to Agent Communication Languages (ACLs). First, we outline the theory of signalling acts. In contrast to current approaches to communication, this account is neither intention-based nor commitment-based, but convention-based. Next, we outline one way of embedding that theory within an account of conversation. We move here from an account of the basic types of communicative act (the statics of communication) to an account of their role in sequences of exchanges in communicative interaction (the dynamics of communication). Finally, we apply the framework to the analysis of a conversational protocol.