Abstract Current, state-of-the-art speaker-independent continuous-speech recognizers are
able to achieve word recognition rates in excess of 94 percent using lexicons of 1000 words
or less and grammars or language models with perplexity 60 or less. Performance of these
systems decreases rapidly as the perplexity of the grammar increases. As we allow users
the flexibility to speak naturally, using constructions of their own choosing, perplexities
increase more than an order of magnitude. Fortunately, knowledge of the domain and of …