10. The computer-readable memory device of claim 9 , wherein the instructions, when executed on the processor, further cause the device to: upon receiving an expression of the dialogue, evaluate the expression of the dialogue according to an expression evaluator to generate at least one dialogue hypothesis involving the expression; and upon identifying a failure to parse the expression of the dialogue according to the expression evaluator, report to the user a parsing error indicating the failure to parse the expression of the dialogue, where the parsing error is different than the action error.
11. The computer-readable memory device of claim 10 , wherein: the expression evaluator further comprises: a language recognizer that identifies at least one language element of the expression, and a language parser that parses the expressions to generate the dialogue hypothesis; and the parsing error is selected from a parsing error set comprising: an expression recognizer error indicating to the user a failure to recognize the expression; and a language parsing error indicating to the user a failure to parse the expression, where the language parsing error is different from the expression recognizer error.