A dialog manager (DM) is a component of a dialog system (DS), responsible for the state and flow of the conversation. Usually:The input to the DM is the human utterance, usually converted to some system-specific semantic representation by the Natural language understanding (NLU) component. For example, in a flight-planning dialog system, the input may look like "ORDER(from=TA,to=JER,date=2012-01-01)". The DM usually maintains some state variables, such as the dialog history, the latest unanswered question, etc., depending on the system. The output of the DM is a list of instructions to other parts of the dialog system, usually in a semantic representation, for example "TELL(flight-num=123,flight-time=12:34)". This semantic representation is usually converted to human language by the Natural language generation (NLG) component.