Modelling structures for situated discourse

Abstract

In this paper, we argue that modelling situated discourse requires not only allowing nonlinguistic events to enter into discourse relations with speech act contents, but also modelling semantic interactions between nonlinguistic events themselves. In an evolving nonlinguistic context, these interactions can give rise to a rich semantic, nonlinguistic structure that is relevant for the interpretation of conversational moves. Examining how these nonlinguistic structures interact with structures determined by dialogue moves reveals new types of discourse structure and a novel perspective on discourse threads and goals. We motivate our arguments with a study of a corpus of situated multiparty chats developed for the STAC project1 and annotated for discourse structure in the style of Segmented Discourse Representation Theory (SDRT; Asher and Lascarides, 2003). The STAC corpus is not only a rich source of data on strategic conversation, but also the first corpus that we are aware of that provides discourse structures for multiparty dialogues situated within a virtual environment. The corpus was annotated in two stages: we initially annotated the chat moves only, but later decided to annotate interactions between the chat moves and non-linguistic events from the virtual environment. This two-step procedure allows us quantify various ways in which adding information from the nonlinguistic context affects dialogue structure.