The use of syntax in a speech understanding system

When a person hears an English sentence, he uses many sources of information to assign structure and meaning to the utterance. One of these sources, syntax, is concerned with the goal of producing a consistent, meaningful, grammatical structure for the sentence. The exact type of structure produced is not as crucial as the process of building that structure because the speech environment has inherent problems which make the parsing of speech a much more complex task than the parsing of text. For example, lexical ambiguity, caused by variations in articulation and imperfect or imprecise phoneme recognition, would lead to a combinatorial explosion in conventional parsers. This paper describes the design of the Bolt Beranek and Newman (BBN) speech parser with emphasis on the reasons for using the formalism of transition network grammars and on the interaction of the syntactic component with other parts of the system. A detailed example is given to illustrate the operation of the parser.