1. A method for developing a semantic understanding of a natural language dialog session involving at least two human participants, the method comprising, with a computing system: receiving a plurality of instances of spoken natural language dialog input supplied by a plurality of human participants in the dialog session; for each of the instances of dialog input, developing an intent, the intent comprising a structured representation of semantic content of the instance of dialog input; storing the intents in a shared dialog context; selecting an intent from the shared dialog context based on an intent mapping, the intent mapping defining a relationship between the selected intent and a current intent, the current intent comprising a structured representation of semantic content of a current instance of dialog input supplied by one of the human participants in the dialog session; creating a shared intent by combining a portion of the selected intent with a portion of the current intent; and executing an action on the computing system in response to the shared intent.