The goal human-machlne of thls w o r k is the enrichment of mteractIons in a natural language envlronment. 1 W e w a n t to provide a f r a m e w o r k less restrictive than earlier ones by allowing a speaker leeway tn forming an utterance about a task and in determining the conversational vehicle to deliver it, A speaker a n d listener cannot be assured to have the s a m e beliefs, contexts, b a c k g r o u n d s or goals at each point in.