... characterizing text structure in terms of the relations that hold between parts of a text (e.g., CONTRAST, MOTIVATION). The defini- tion of each RST relation includes constraints on the two ... follow-up questions in the context of the on- going conversation and to determine how to clarify a response when necessary. To pro- vide these capabilities, an explanation facility must ... attentional information to produce coherent text (McKeown, 1985, McCoy, 1985, Paris, 1988b), omitting intentional informa- tion, or conflating intentional and rhetorical information (Hovy,...