  Research in discourse processing has identified two representational
requirements for discourse planning systems. First, discourse plans must
adequately represent the intentional structure of the utterances they produce
in order to enable a computational discourse agent to respond effectively to
communicative failures \cite{MooreParisCL}. Second, discourse plans must
represent the informational structure of utterances. In addition to these
representational requirements, we argue that discourse planners should be
formally characterizable in terms of soundness and completeness.
