Handling Speech Repairs and Other Disruptions Through Parser Metarules
Mark G. Core, Lenhart K. Schubert · 2002
Mixed-initiative dialogs often contain interruptions in phrase structure such as repairs and backchannel re-sponses. Phrase structure as traditionally defined does not accommodate such phenomena, so it is not sur-prising that phrase structure parsers are ill-equipped to handle them. This paper presents metarules that specify how phrase structure rules may be restarted or interrupted (including overlapping speech). In the case of overlapping speech or a backchannel response, the metarules allow a constituent to overlap or be em-bedded inside another constituent that it is uncon-nected to. In the case of repairs, the metarules operate on the reparandum (what is being repaired) and alter-ation (the correction) to build parallel phrase struc-ture trees: one with the reparandum and one with the alteration. Consider the utterance, take the ban-um the oranges. The repair metarule would build two VPs, one being take the ban- and the other being take the oranges. The introduction of metarules simpli-fies the notion of an utterance since a sentence inter-rupted by an acknowledgment such as okay can still be one utterance formed around the interrupting ac-knowledgment. Together metarules and phrase struc-ture rules specify the structures that should be accom-modated by a parser for mixed initiative dialogs. A dialog parser should also maintain a dialog chart that stores the results of syntactic and semantic analysis of all of the dialog seen so far. This dialog chart will be a shared resource eliminating the need for mainte-nance of a separate representation of dialog structure by a dialog manager. In addition, the dialog parser can alert the dialog manager to utterances introduc-ing obligations as well as recognizing acknowledgments and responses based on syntactic information.