1. A method comprising: receiving, by a task completion service, an input comprising information in a natural language; determining, by a dialog manager of the task completion service, an intent of the input; determining, by the dialog manager, target information to fulfill the intent; identifying, by the dialog manager, one or both of information among the target information that is available to the dialog manager or information among the target information that is not available to the dialog manager; generating a conversational understanding document comprising the intent and the identified information; and forwarding the conversational understanding document to a task completion handler separate from the dialog manager.