Spoken Dialogue Systems are automatic systems that interact with humans (or other systems) by accepting spoken language input and producing spoken language output. Spoken language input is handled by speech recognition, and language analysis and understanding components. Spoken language output is achieved by playback of recorded human speech, or by speech synthesis. Spoken dialogue systems include a component for dialogue control, which may make use of artificial intelligence techniques. Spoken dialogue systems are widely used for information and transaction systems, such as stock market information or travel reservation.