1. A method for processing discourse input comprising: at an electronic device with a processor and memory storing one or more programs for execution by the processor: receiving a discourse input from a user; determining a text string corresponding to the discourse input, wherein determining the text string comprises: determining, using a first language model, a conditional probability of a candidate word in the discourse input given one or more words in the discourse input; determining, using a second language model, a probability of the candidate word within a corpus; determining, using a third language model, a conditional probability of the candidate word given one or more classes associated with the one or more words; and determining an integrated probability of the candidate word and one or more subclasses associated with the candidate word based on: the conditional probability of the candidate word given the one or more words; the probability of the candidate word within the corpus; and the conditional probability of the candidate word given the one or more classes, wherein the text string is based on the integrated probability; and generating an output based on the text string.