20. The method of claim 18 wherein the natural language input is represented by a speech signal and further comprising: performing speech recognition on the speech signal prior to performing statistical classification.
18. A computer-implemented method of processing a natural language input for use in completing a task represented by the natural language input, comprising: generating a feature vector based on the natural language input; performing statistical classification on the feature vector with a processor to obtain a class identifier identifying a target class associated with the natural language input, the statistical classification being performed by performing statistical classification on the natural language input using a plurality of different statistical classifiers, and selecting the class identifier output by a greatest number of the plurality of statistical classifiers as representing the target class; selectively activating grammar rules in a grammar used in a rule-based analyzer, the activated grammar rules corresponding to the class identifier; and analyzing the natural language input with the rule-based analyzer using the grammar with the activated grammar rules to generate semantic expressions from the natural language input to fill semantic slots in the target class.