18. One or more computer-readable storage media, having computer-executable instructions which, when executed by at least one processor, perform a method for building a statistical model for contextual language understanding, comprising: receiving a first natural language expression, wherein the first natural language expression includes at least one of words, terms, and phrases; performing a first action based on a first prediction determined by a single-turn model and a second prediction determined by a multi-turn model; receiving a second natural language expression, wherein the second natural language expression includes at least one of words, terms, and phrases; evaluating at least the first natural language expression, the first action, the first prediction, the second prediction, and the second natural language expression to generate contextual information; aggregating the contextual information into the multi-turn model; and performing a second action based on evaluating at least the first natural language expression, the first action, the first prediction, the second prediction, and the second natural language expression.
18. One or more computer-readable storage media, having computer-executable instructions which, when executed by at least one processor, perform a method for building a statistical model for contextual language understanding, comprising: receiving a first natural language expression, wherein the first natural language expression includes at least one of words, terms, and phrases; performing a first action based on a first prediction determined by a single-turn model and a second prediction determined by a multi-turn model; receiving a second natural language expression, wherein the second natural language expression includes at least one of words, terms, and phrases; evaluating at least the first natural language expression, the first action, the first prediction, the second prediction, and the second natural language expression to generate contextual information; aggregating the contextual information into the multi-turn model; and performing a second action based on evaluating at least the first natural language expression, the first action, the first prediction, the second prediction, and the second natural language expression. 19. The computer-readable storage media of claim 18 , wherein the second action is a response to at least one of the first natural language expression and the second natural language expression.