15. A system for providing a statistical initial topic classification model for use in a natural language call routing application to map a natural language user statement to at least one of a plurality of topics in the natural language call routing application, comprising: at least one processor programmed to; access a voice user interface (VUI) specification that specifies a VUI for allowing users to interact with the natural language call routing application, the VUI specification comprising a plurality of expressions of possible user intentions composed by at least one VUI designer, the VUI specification further comprising, for each one of the plurality of expressions of possible user intentions, at least one system response or action defined by the at least one VUI designer as corresponding to the one of the plurality of expressions of possible user intentions; analyze the VUI specification to determine a plurality of topic descriptions, each one of the plurality of topic descriptions describing a meaning of a corresponding one of the plurality of topics; and use, as training data, the plurality of topic descriptions determined by analyzing the VUI specification to build the statistical initial topic classification model, comprising; identifying keywords in the plurality of topic descriptions used as training data to build the statistical initial topic classification model; providing an optimal feature set comprising at least one combination of at least some of the keywords; and building the statistical initial topic classification model based at least partially on the optimal feature set.
17. The system of claim 15 , wherein, for at least one topic in the plurality of topics, a corresponding topic description comprises no more than two natural language sentences describing the at least one topic.