ATIS Domain Research Articles

Characterizing speech timing and speaking rate through subword parse trees

A sublexical parse tree is used to model and study characteristics of speech timing in English. This representation is based on the ANGIE system [Seneffet al., Proc. ICSLP (Philadelphia, PA, 1996)], a hierarchical framework which captures morphological, syllabic, and phonological phenomena probabilistically. The duration of a unit in the tree is measured as a percentage of the total duration of its corresponding parent unit. This framework can be used both to conduct statistical studies to characterize temporal phenomena and to create duration models to aid speech recognition. A strategy has been developed in which unit durations in upper layers are successively normalized by their respective realizations in the layers below. This reduces the variance at each unit by enabling the sharing of statistical distributions to overcome sparse data problems. The normalized duration of a word node at the top of the tree can be taken as a parameter for speaking rate. The data were used to examine within-speaker rate variability and to study the second-order effects of speaking rate on relative durations of sublexical units. The experiments are being conducted in the ATIS domain [Glass et al., Proc. ARPA Spoken Language Technology Workshop, TX (1995), pp. 252–256].

PEGASUS: A spoken dialogue interface for on-line air travel planning

This paper describes PEGASUS, a spoken dialogue interface for on-line air travel planning that we have recently developed. PEGASUS leverages off our spoken language technology development in the ATIS domain, and enables users to book flights using the American Airlines EAASY SABRE system. The input query is transformed by the speech understanding system to a frame representation that captures its meaning. The tasks of the System Manager include transforming the semantic representation into an EAASY SABRE command, transmitting it to the application backend, formatting and interpreting the resulting information, and managing the dialogue. Preliminary evaluation results suggest that users can learn to make productive use of PEGASUS for travel planning, although much work remains to be done.

Linking speech and language processing through prosody

In most spoken language understanding systems today, the interface between speech recognition and natural language processing is little more than a serial connection. The top scoring recognition results (a list of sentence hypotheses) are passed to the natural language system, which typically processes these taking the highest ranking recognition hypothesis that is interpretable and ignoring any acoustic information other than rank. The system can be improved by choosing the utterance interpretation based on a combination of the acoustic likelihood of a hypothesized word string and an associated language score (e.g., parse probability or semantic preference score). However, further gain is offered by incorporating a prosody score as well, since prosody can provide a link between syntactic/semantic structure and certain types of acoustic variability. In this talk, two types of computational models of prosody will be described that integrate acoustic cues with text features based on recognizer sentence hypotheses and associated parser outputs. Also, methods for using prosodic information in automatic speech understanding systems will be described. Experimental results with speech understanding in the ATIS domain will be described for three different aspects of prosody: prosodic phrasing, prominence placement, and cues to disfluencies. [Work supported by NSF and ARPA.]