Bidirectional charts: a potential technique for parsing spoken natural language sentences

Abstract The use of “high level” knowledge sources in recognizing continuous speech is aimed at reducing the hypothesis space generated by acoustic-phonetic analysis. In this, a sentence parser can be a basic resource, provided that it can deal with the ambiguity of the input and with the fact that fragments may have been recognized even hypothetically. One of the most successful techniques for parsing natural language is chart parsing. Chart parsing is directional in the sense that it works from a starting point (usually the beginning of the sentence) and usually proceeds to the right. We describe the concept of a chart that works outward from islands (reliably recognized fragments), makes sense of as much of the sentence as possible, and then goes on to make predictions about missing fragments.