14. A natural language understanding (NLU) system comprising: a computer comprising at least one processor configured to perform acts of: categorizing an NLU application to produce an application categorization having a plurality of categories; classifying an NLU database corpus of example expressions to produce a classified corpus by identifying at least one of the categories for each example expression of the example expressions; and building from the classified corpus a first language model configuration comprising a first statistical language model; evaluating an interpretation accuracy of the first language model configuration using test data; determining whether the evaluated interpretation accuracy is less than a desired accuracy; when it is determined that the evaluated interpretation accuracy is at least the desired accuracy, then adopting the first language model configuration; and when it is determined that the evaluated interpretation accuracy is less than the desired accuracy, then: sub-dividing the application categorization into a plurality of sub-categories; and building a second language model configuration comprising a plurality of statistical language models corresponding to the plurality of sub-categories.
17. The NLU system of claim 14 , further comprising: a visual toolkit having a graphical user interface (GUI) for visually presenting said application categorization and classifying said NLU database corpus.