1. A method for scaling a language understanding system, comprising: receiving, by a computing device, an utterance using the language understanding system; detecting, by the computing device, a plurality of domains that are associated with the utterance; detecting, by the computing device, a plurality of actions from the utterance for each detected domain of the plurality of domains; associating, by the computing device, each action of the plurality of actions with one or more of the detected plurality of domains; detecting, by the computing device, a plurality of objects from the utterance for each detected action of the plurality of actions; training at least one model by applying a threshold hypothesis to at least one stage from a model manager, whereby training data is shared across different domains supported by the language understanding system; and performing, by the computing device, slot filling, wherein at least one slot is filled, the at least one slot further defining at least one of the plurality of domains or the plurality of objects.