1. An authoring component configured for generating components for use in mapping natural language inputs to slots and preterminals derived from a schema in a natural language understanding (NLU) system, the authoring component comprising: a model trainer implemented using a processor of a computer, wherein the model trainer obtains a schema indicative of a task to be completed, the schema including a plurality of slots and a plurality of preterminals configured to be filled with portions of a natural language input, the preterminals comprising at least one of a preamble and postamble associated with one or more of the slots, and wherein the model trainer is configured to train a rules based grammar, based on training data, for mapping terms from the natural language input to slots derived from the schema and to train a plurality of statistical models for mapping terms from the natural language input to the preterminals derived from the schema, wherein the model trainer is configured to train a statistical model corresponding to each of a plurality of different preterminals, wherein the model trainer receives the training data and enumerates segmentations of the training data to associate the slots and preterminals with the training data, wherein the model trainer is configured to train a statistical model for each preterminal derived from the schema using the text associated with each preterminal as training data for the statistical model for that preterminal.
7. The authoring component of claim 1 and further comprising: a probabilistic library grammar accessible by the model trainer.