Dialogue systems employed one or more of text, speech, graphics, haptics, gestures, and other modes for communication on both the input and output channel.
The elements of a dialogue system are not defined because this idea is under research,[citation needed] however, they are different from chatbot.
However, the mere existence of mixed-initiative is not sufficient to be classified as a natural dialogue system.
Therefore, NADIA (a research prototype) gives an idea of how to fill that gap and combines some of the aforementioned aspects like natural language generation, adaptive formulation, and sub dialogues.
Dialogue systems can support a broad range of applications in business enterprises, education, government, healthcare, and entertainment.