IN THE HEARSAY-II SPEECH UNDERSTANDING SYSTEM

The Hearsay‐II System has as its design goal recognition, understanding, and responding to connected speech utterances, particularly in situations where sentences cannot be guaranteed to agree with some predefined, restricted language model, as in the case of the Harpy System. Further, it attempts to view knowledge sources as different and independent which cannot always be integrated into single representation. It is based on the blackboard model [V. R. Lesser, R. D. Fennell, L. D. Erman, and D. R. Reddy, IEEE Trans. Acoust. Speech and Signal Process. ASSP‐23, 11–23 (1975) with knowledge sources as a set of parallel processes which are activated asynchronously depending on data events. The system performs on the Information Retrieval task with accuracy comparable to that of the Harpy system, but runs about 2 to 20 times slower. More complete performance results will be reported. As we get closer to unrestricted vocabularies and nongrammaticality of spoken languages, it will be necessary to have systems w...