Discourse Processing of Dialogues with Multiple Threads

In this paper we will present our ongoing work on a plan-based discourse processor developed in the context of the Enthusiast Spanish to English translation system as part of the JANUS multilingual speech-to-speech translation system. We will demonstrate that theories of discourse which postulate a strict tree structure of discourse on either the intentional or attentional level are not totally adequate for handling spontaneous dialogues. We will present our extension to this approach along with its implementation in our plan-based discourse processor. We will demonstrate that the implementation of our approach out-performs an implementation based on the strict tree structure approach. 1 Introduction In this paper we will present our ongoing work on a plan-based discourse processor developed in the context of the Enthusiast Spanish to English translation system (Suhm et al. 1994) as part of the JANUS multilingual speech-to-speech translation system. The focus of the work reported here has been to draw upon techniques developed recently in the computational discourse processing community (Lambert 1994; Lambert 1993; Hinkelman 1990), developing a discourse processor flexible enough to cover a large corpus of spontaneous dialogues in which two speakers attempt to schedule a meeting. There are two main contributions of the work we will discuss in this paper. From a theoretical standpoint , we will demonstrate that theories which postulate a strict tree structure of discourse (henceforth, Tree Structure Theory, or TST) on either the intentional level or the attentional level (Grosz and Sidner 1986) are not totally adequate for covering spontaneous dialogues, particularly negotiation dialogues which are composed of multiple threads. These are negotiation dialogues in which multiple propositions are negotiated in parallel. We will discuss our proposea extension to TST which handles these structures in a perspicuous manner. From a practical standpoint, our second contribution will be a description of our implemented discourse processor which makes use of this extension of TST, taking as input the imperfect result of parsing these spontaneous dialogues. We will also present a comparison of the performance of two versions of our discourse processor, one based on strict TST, and one with our extended version of TST, demonstrating that our extension of TST yields an improvement in performance on spontaneous scheduling dialogues. A strength of our discourse processor is that because it was designed to take a language-independent meaning representation (interlingua) as its input, it runs without modification on either En-glish or Spanish input. Development …