Implementing Parser Metarules that Handle Speech Repairs and Other Disruptions
Mark G. Core, Lenhart K. Schubert · 1998
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 the instantiations of phrase structure rules may be restarted or interrupted, with allowance for in-terleaved speech. In the case of interleaved speech or backchannel responses, tlle metarules allow syntacti-cally separate constituents to interleave or to strad-dlc each other. In the case of repairs, the metarules operate on the reparandum (what is being repaired) and alteration (the correction) to build parallel phrase structure trees: one with the reparandum and one with the alteration. Consider the partial utterance, take the ba~- 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 simplifies the notion of an utterance since a sentence interrupted by an acknowledgment such as okay can stiU be treated as a single utterance formed around the interrupting acknowledgment. Together, metarules and phrase structure rules specify the struc-tures that should be accommodated by a parser for mixed initiative dialogs. A dialog parser should also maintain a dialog chart that stores the results of syn-tactic and semantic analysis of all the dialog seen so far. This dialog chart will be a shared resource elim-inating the nced for maintenance of a separate repre-sentation of dialog structure by adialog manager.