Automatic speech understanding must accomodate the fact that an entirely accurate and precise aco-tstic transcription of speech is unattainable. By applying knowledge about the phonology, syntax, and semantics of a language and the constraints imposed by a task domain, much of the ambiguity in an attainable transcription can be resolved. This paper deals with how to control the application of such knowledge. A control framework is presented in which hypotheses about the meaning of an utterance

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... re automatically formed and evaluated to arrive at an acceptable interpretation c' v .he utterance. This design is currently undergoing computer implei.tentation as a part of the BBN Speech understanding System (SPEECHLIS).