A Framework for Processing Corrections in Task-Oriented Dialogues

Mundane discourse abounds with utterances referring to other utterances. These meta-language utterances appear with surprising frequency in task-oriented dialogues, such as those arising in the context of a natural language interface to an operating system. This paper identifies some simpler types of dialogue-level meta language utterance and provides a computational framework to process such phrases in the context of a case-frame parser exploiting strongly-typed domain semantics. 1 . I n t r o d u c t i o n ivteta-language utterances, i.e. utterances about other utterances in the discourse context, have received little attention in the computational linguistic literature. Yet, as a recent attempt [1] to create a taxonomy of discourse-level metal inguist ic devices shows, such utterances are ubiquitous in all kinds of dialogues, including task-oriented man-machine dialogues through a natural language interface. Indeed, in a recent informal experiment with a simulated natural language command interface to a computer operating system, we found that one out of every twelve inputs was a meta language utterance of one type or another. Meta language utterances fall into two primary categories, intra sentential and extra sentential (dialogue level) utterances. The former class may be divided into referential and interpretive meta-linguistic devices. For instance: "Load, read and rewind the tape in tha t o rde r . " is a typical referential intra-sentential meta language utterance of the kind that has received some attention in the linguistics literature [8, 6]. "In that order" refers to the surface structure sequencing of the lexical items denoting the commands. Interpretive meta language utterances make a statement about how another portion of that utterance should be interpreted, for instance: " M e t a p h o r i c a l l y s p e a k i n g , John's ideas are out of this wor ld. " Discourse-level metal inguist ic utterances refer to utterances or portions of utterances outside the scope of the immediate sentence. For instance, the third utterance in the dialogue fragment below is essentially a correction of a previous utterance. USER: Print gauss.rel on the diablo printer. SYSTEM: GAUSS.REL is not a printable file. USER: Oops, I meant gauss.for This paper focuses on developing a process model for certain classes of dialogue-level meta language utterances, which occur in task-oriented dialogues with greater frequency than intrasentential ones. With the exception of the analysis and classification of dialogue-level metal inguist ic utterances i n [1 ] , there is little prior analysis of this phenomenon, although work in discourse focus [2, 10] and indirect speech acts [9, 7] is of direct relevance in analyzing the general phenomenon. We currently have no general process-level theory for metalanguage comprehension, but we have developed a framework for dealing with an important common subset of discourse-level meta language utterances: those that repair errors or misunderstandings that arose earlier in the dialogue, such as "I meant to say transfer, not copy" ,