Display device and artificial intelligence system

An artificial intelligence (AI) system for providing a voice recognition service, the AI system comprising:

• a display device configured to:
• receive a starting command uttered by a user, the starting command being a voice command to activate an AI agent providing a voice recognition service, identify a first AI agent corresponding to the received starting command display a first UI for representing the identified first AI agent, receive an operating command uttered by the user, the operating command being for controlling a specific operation of the display device;
• and
• a natural language process, NLP, server configured to:
• receive voice data corresponding to the operating command from the display device, convert the received voice data into text data, acquire, by a first AI agent of the NLP server, a user intent of the text data, if the first AI agent determines that it is not able to process the user intent of the text data, transmit, by the first AI agent, the text data to a second AI agent of the NLP server and acquire, by the second AI agent of the NLP server, a user intent of the text data, receive an intent fulfillment result, identify which AI agent provides the intent fulfillment result, determine whether the identified AI agent is identical to the first AI agent corresponding to the starting command, and if the identified AI agent is not identical to the first AI agent, transmit an AI agent change notification and the intent fulfillment result to the display device,
• wherein the display device is further configured to:
• change the first UI to a second UI for representing the second AI agent, if the AI agent change notification is received, and display the second UI and the intent fulfillment result based on the AI agent change notification and the intent fulfillment result.