  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 multi-lingual 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 outperforms an implementation based on the strict tree
structure approach.
